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#1 2005-04-01 20:27:42

sskl
Member
Registered: 2005-03-26
Posts: 4

need help!!!

Q1. Divide 64 into two parts so that the difference bettween 2/3 of one part and 1/4 of the other is equal to 28. What is the value of the larger part?

i hv did a little bit on tis qn... but i m stuck or isit i m wrong...
my working: let the larger no. be x.
let the smalelr no. be 64/x.
2/3x - 1/4(64/x) = 28
2/3x - 64/4x = 28
8x/12 - 192/12x = 28
i m stuck here...

Q2. A boy walks a certain distance at 9km/h. He finds that if he increases his speed by 1/3, he would have saved 4/3 hrs. Find the distance he walks.

for tis qn, i dun reli undertsand or know how 2 solve it... yarr...:|

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#2 2005-04-01 22:48:52

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

Q1.

Full credit for having a go at it! You are using a good method, but I think the confusion is at the beginning. "Divide 64 into two parts" could mean "x times y equals 64" (as you thought of it), or "x plus y equals 64" (as in "let's divide this cake")

It works out neatly if you think of it as "x plus y equals 64"

So we can write it down as:

x+y=64
and
(2/3)x - (1/4)y = 28 (like you had it)

Let's solve:
x+y=64
y = 64-x
So: (2/3)x - (1/4)(64-x) = 28
then: (2/3+1/4)x - (1/4)64 = 28
(8/12+3/12)x - 16 = 28
(11/12)x=44
x= 44*12/11 = 4*12 = 48

Check it for me smile


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#3 2005-04-01 23:10:26

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

Q2. A boy walks a certain distance at 9km/h. He finds that if he increases his speed by 1/3, he would have saved 4/3 hrs. Find the distance he walks.

I agree, it is hard to get your head around it.

Let's rephrase a little: 9km/h times (1+1/3) saves 4/3h, or an extra 3km/h saves 4/3h, so his time "t" is reduced.

OK, I think I can work this ... it has TWO things we don't know, time AND distance.

Let's call time "t" (in hours), and distance "x" (in km)

x = 9t (he went at 9km/h)
x = 9(1+1/3)(t-4/3) (increasing speed by 1/3 reduces time by 4/3)

Put the two together:

9t = 9(1+1/3)(t-4/3)
9t = 12(t-4/3)
9t = 12t-48/3
9t = 12t-16
-3t = -16
t = 16/3

Check this, too smile


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#4 2005-04-04 21:55:44

sskl
Member
Registered: 2005-03-26
Posts: 4

Re: need help!!!

gee... for question 1, i had checked and u are right! thank you... so my confusion is on the divide 64 into 2parts... thx alot!!:lol:
but for question 2, i have not check yet... sorry... i will try to find the time to check.... thx anyway...

Last edited by sskl (2005-04-04 21:56:29)

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#5 2005-04-05 07:30:06

dannyk
Member
Registered: 2005-04-05
Posts: 1

Re: need help!!!

I have forgotten how to find the square root of numbers by hand (without the use of a calculator), can anyone help me?
                                                                                                                                                                 Thanks  Dannyk

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#6 2005-04-05 09:20:19

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

Example: Square Root of 2 (but works generally)

Guess: 1.5

2/1.5 = 1.333
Average the guess and the answer: (1.5+1.333)/2 = 1.417

Again:
2/1.417 = 1.411
Average the guess and the answer: (1.417+1.411)/2 = 1.414    DONE!   

So, the more times you do this, the more accurate it becomes, but you can see that we have quickly arrived at three decimal places of accuracy. Stuff like this is called Successive Approximation.


Let's try another one. Square root of 10

Guess: 4
10/4=2.5
(4+2.5)/2 = 3.25
10/3.25=3.077
(3.25+3.077)/2 = 3.163
Test: 3.163*3.163 = 10.004 Amazing!

This can be useful if you are stuck without a calculator and need to find the diagonal of a square. I used it once for placing survey pegs in the ground when I was far from home.


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#7 2005-04-13 22:41:13

classhelp
Member
Registered: 2005-04-13
Posts: 1

Re: need help!!!

i dont know how to divide numbers without the use of calculators but am embarassed to ask infront of my class, for example 19.50 / 83. please help me. roll

Last edited by classhelp (2005-04-13 22:44:51)

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#8 2005-04-13 22:55:16

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

Oh, you need a calculator for that !

Just kidding smile

19.5 / 83 would probably need long division. DECIMAL long division !

Looking at it, it would probably be easier written as 195/830  (it is the same, because I multiplied top AND bottom by the same number - 10)


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#9 2005-04-13 23:00:53

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

So, we are asking how many 830s go into 195

It is going to be less than 1, so we need to put some extra decimal places:

830 ) 195.000

First step is to guess where to start. Largest multiple of 830 that isn't TOOO big. 2 x 830 = 1660, so 0.2 x 830 = 166 is a good starting point"

            0.2
830 ) 195.000
         166.000

Now we have see how much is left to go:

            0.2
830 ) 195.000
         166.000
           29.000

So let's work on the 29: 3 x 830 = 2490:

            0.23
830 ) 195.000
         166.000
           29.000
           24.9
             4.1

So let's work on the 4.1: 4 x 830 = 3320:

            0.234
830 ) 195.000
         166.000
           29.000
           24.9
             4.10
             3.32
             0.78

Ohh, thats far enough !!   

19.5 / 83 = 195/830 = 0.234


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#10 2005-04-13 23:02:30

insomnia
Real Member
Registered: 2005-03-23
Posts: 944

Re: need help!!!

Go on then


Friends are angels who lift our feet when our own wings have trouble remembering how to fly

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#11 2005-04-13 23:13:05

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

Did I get it right, insomnia?

I just type and type, and hope I get it right


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#12 2005-04-14 00:18:55

insomnia
Real Member
Registered: 2005-03-23
Posts: 944

Re: need help!!!

It's 0.235, rounded up. So, you were close


Friends are angels who lift our feet when our own wings have trouble remembering how to fly

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#13 2005-04-14 00:23:37

Zach
Member
Registered: 2005-03-23
Posts: 2,075

Re: need help!!!

You sad person.


Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.

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#14 2005-04-14 00:24:12

insomnia
Real Member
Registered: 2005-03-23
Posts: 944

Re: need help!!!

You told me to do it!!!?


Friends are angels who lift our feet when our own wings have trouble remembering how to fly

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#15 2005-04-14 00:27:33

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

OK, good enough. So long as it wasn't the PM figuring the next Budget I'm safe.


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#16 2005-04-14 00:31:21

Zach
Member
Registered: 2005-03-23
Posts: 2,075

Re: need help!!!

They know budgets?


Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.

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#17 2005-04-14 00:33:42

insomnia
Real Member
Registered: 2005-03-23
Posts: 944

Re: need help!!!

Some of them do. only like 3 people. They are all like secretaries,etc. No-one important knows.


Friends are angels who lift our feet when our own wings have trouble remembering how to fly

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#18 2005-04-14 00:36:25

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,535

Re: need help!!!

So they come here when the calcs get too hard.


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#19 2005-04-14 00:37:58

Zach
Member
Registered: 2005-03-23
Posts: 2,075

Re: need help!!!

Evil laughter?


Boy let me tell you what:
I bet you didn't know it, but I'm a fiddle player too.
And if you'd care to take a dare, I'll make a bet with you.

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#20 2005-04-14 00:38:28

insomnia
Real Member
Registered: 2005-03-23
Posts: 944

Re: need help!!!

Yep. They use you. You think they are maths questions, but in fact you are deciding the budget for them. But, they can't read and get it wrong and screw up the country


Friends are angels who lift our feet when our own wings have trouble remembering how to fly

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#21 2005-04-14 03:17:03

E=tally=3
Guest

Re: need help!!!

budget people use this site!! wow!!!  i am coming here all the time. i can talk tot hem about how this country is annoying, with its silly governments.

the prime minister here!!   that is amazing!  am a baffled that they come here...   amazing!!!!!

#22 2005-04-14 03:19:48

Mr T
Member
Registered: 2005-03-30
Posts: 1,012

Re: need help!!!

shut up


I come back stronger than a powered-up Pac-Man big_smile
I bought a large popcorn @ the cinema the other day, it was pretty big...some might even say it was "large
cool Fatboy Slim is a Legend cool

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#23 2005-04-14 05:37:34

static helper
Member
Registered: 2005-04-14
Posts: 27

Re: need help!!!

thats not nice  BOOHOO.  plz be nice. Or ill be mean to you


Vote Stewie smile and Mr T smile and static helper smile

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#24 2005-04-14 05:41:14

static helper
Member
Registered: 2005-04-14
Posts: 27

Re: need help!!!

i was E=tally=3 last time, i didnt log in


Vote Stewie smile and Mr T smile and static helper smile

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#25 2005-04-14 05:50:22

Mr T
Member
Registered: 2005-03-30
Posts: 1,012

Re: need help!!!

sorry, i didn't know. it is my job to be mean to guests so that they join to hurl abuse at me. xcessive maths nerd is an example of this


I come back stronger than a powered-up Pac-Man big_smile
I bought a large popcorn @ the cinema the other day, it was pretty big...some might even say it was "large
cool Fatboy Slim is a Legend cool

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