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#1 2006-08-15 17:29:35

Fat_nerd
Guest

Help with questions~

I need help with some math questions...please help roflol


Q1 A motorcyclist and a cyclist travel from A to B and leave simultaneously from A at 12 noon. The motorcyclist arrives at B after 1.5hours and cyclist arrives 30minutes later. At what time was the cyclist twice as far from B as the motorcyclist was?


Q2 When 3 sqaures are drawn so that sides are shared there are two figures which can be constructed.


Q3 Mouldy Oldy claims that if trhe digits in his age are multiplied, the result would be eqaul to his age 40years ago. How old is Mouldy Oldy.


Please show me the working out smile .

#2 2006-08-15 22:45:17

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Help with questions~

1.

So, the motorcylist and cylist are both travelling at constant speeds, right? OK then.
Let's say that B is 60 miles from A, because that makes the numbers nice. This way, the motorcylist is travelling at 40mph and the cylist at 30.

The distance of the motorcylist from B at any time is given by 60 - 40t, when 0<t<1.5.
Similarly, the distance of the cylist is given by 60 - 30t, when 0<t<2.

The equation we need to solve is 2(60 - 40t) = 60 - 30t.
Multiplying out of brackets gives 120 - 80t = 60 - 30t.
Simplifying: 60 = 50t.
Solving: t = 60/50 = 1 hour, 12 minutes.
At that time, the motorcylist is 12 miles away and the cylist is 24 miles away.

2. I'm not sure what this question is asking. Could you explain it in more detail please?

3.

Mouldy Oldy's age can be written as 10a+b, where a is the 10's digit of his age and b is the units digit.

The equation here is ab + 40 = 10a + b.
This is trickier, because we have one equation but 2 variables. But we also have the constraints that a and b are integers and between 0 and 9, which should help out.

If we rearrange to find a in terms of b, we should be able to try out some numbers for b and see which ones return sensible a values.

ab + 40 = 10a + b
ab - 10a = b - 40
a(b - 10) = b - 40
a = (b - 40)/(b - 10)

This table shows what value of a is returned when all the possible b values are tried.

        a   |    b
     ---------------
       4.3  |    1
       4.8  |    2
       5.3  |    3
       6     |    4
       7     |    5
       8.5  |    6
       11   |    7
       16   |    8
       39   |    9
        4    |    0

Of these, 3 solutions are valid. Therefore, Mouldy Oldy is either 64, 75 or 40.


Why did the vector cross the road?
It wanted to be normal.

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#3 2006-08-16 14:23:27

pi man
Member
Registered: 2006-07-06
Posts: 251

Re: Help with questions~

Q2 When 3 sqaures are drawn so that sides are shared there are two figures which can be constructed.


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#4 2006-09-19 15:40:36

Chelsea
Member
Registered: 2005-06-16
Posts: 390

Re: Help with questions~

Q3 Answer 20, 2x2=4 0x0=0 which equals 40 so the answer is 20.


Theres no other place like home or is there..............

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#5 2006-09-19 15:41:46

Chelsea
Member
Registered: 2005-06-16
Posts: 390

Re: Help with questions~

oh by the way  pi man want to chat about maths because you are the only other member online?


Theres no other place like home or is there..............

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