quadratic formula problems? D:

lalla · 2009-03-23 07:16:27

Hey im having trouble with these problems, and i think were supposed to use the quadratic formula somewhere? not sure D: ..

1. The hypotenuse of a right angled triangle is 15 cm. The sum of the other two sides is 21 cm. Find the lengths of the other two sides.

2. a lidless box is to be constructed from a square peice of tin by cutting a 10 cm square from each corner and bending up the sides for the box. If the volume of the box is 1200cm3, find the dimentions of the original sheet of tin.

LASTLY,
3.computer software programs are sold to students for $20 each. 300 students are willing to buy them at this price. for each $5 increase in price, there are 30 fewer students wiling to buy the software. what price of software will generate $7200 in sales?

THANKS(:

LuisRodg · 2009-03-23 07:38:37

Last edited by LuisRodg (2009-03-23 07:54:28)

lalla · 2009-03-23 07:53:40

oh thanks, and yeah im pretty sure lol

LuisRodg · 2009-03-23 07:54:57

Which one is it?

lalalalaa · 2009-03-23 07:58:29

ops, area.

lalala · 2009-03-23 07:59:04

wait makes more sense with length, SORRY

integer · 2009-03-24 00:06:19

The quadratic formula can be used to answer all three.
If you know it, then no problem.
If you don't understand it ....

Side Note: Question 3.
The unit_price relative to the quantity_sold is rarely linear.
Go in the other direction: at $0 cost you have a limited distribution of 420 students.

smiyc86 · 2009-03-26 16:46:02

lalla wrote:

Hey im having trouble with these problems, and i think were supposed to use the quadratic formula somewhere? not sure D: ..
1. The hypotenuse of a right angled triangle is 15 cm. The sum of the other two sides is 21 cm. Find the lengths of the other two sides.
2. a lidless box is to be constructed from a square peice of tin by cutting a 10 cm square from each corner and bending up the sides for the box. If the volume of the box is 1200cm3, find the dimentions of the original sheet of tin.
LASTLY,
3.computer software programs are sold to students for $20 each. 300 students are willing to buy them at this price. for each $5 increase in price, there are 30 fewer students wiling to buy the software. what price of software will generate $7200 in sales?
THANKS(:

1. try to learn few pythagorean triplets... the most basic one is 3:4:5 ... now if 3:4:5 is a pyth. triplet then 3x:4x:5x is also a triplet .... now for this triplet the hyp:(sum of the other two sides) = 5x:7x =

in this case it is true .... 15:21 = 5*3:7*3

so the other two sides are 3*3 and 4*3 = 9,12

smiyc86 · 2009-03-26 16:50:43

for the 2nd one .... if u visualise , the height of the box = side of the square pieces which are cut out = 10 cm

hence the base area of the box = 120 cm^2
now as the base of the box will also be a square, hence the side of the base of the box = √120 = 2√30

the original side of the tin plate = 2√30 + 10 cm ....

smiyc86 · 2009-03-26 17:05:18

for the last one .....

let $5 be increased x times ... then 30x students are reduced ...

the equation can be formed as:

(20 + 5x)(300 - 30x) = 7200
=> (x-10)(x+4) + 48 = 0

=> x = 2,4

so the prices that will generate $7200 sales will be : $30, $40

Math Is Fun Forum

#1 2009-03-23 07:16:27

quadratic formula problems? D:

#2 2009-03-23 07:38:37

Re: quadratic formula problems? D:

#3 2009-03-23 07:53:40

Re: quadratic formula problems? D:

#4 2009-03-23 07:54:57

Re: quadratic formula problems? D:

#5 2009-03-23 07:58:29

Re: quadratic formula problems? D:

#6 2009-03-23 07:59:04

Re: quadratic formula problems? D:

#7 2009-03-24 00:06:19

Re: quadratic formula problems? D:

#8 2009-03-26 16:46:02

Re: quadratic formula problems? D:

#9 2009-03-26 16:50:43

Re: quadratic formula problems? D:

#10 2009-03-26 17:05:18

Re: quadratic formula problems? D:

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