Pre Algebra Help please...!?

Question

A photo that measures 5in. by 7in. is inlarged to 7.5 in by B in. What is B???
Also.....What is the percent of change??
60 to 36, 18 to 24, 15 to 25, 85 to 50, 8.8 to 30, 1.2 to 0.2?

Answer 1

its all about proportions.
5 - 7
7.5-X
Crossmultiply 7.5x7=5X
divide by 5

Answer 2

I think the 5" width is the one increased to 7.5", which is a 50% increase (50% of 5" is 2.5" and 5 = 2.5 = 7.5). Therefore, to increase 7" by 50% you need to multiply by either 50% and add the result to 7 or easier--just multiply 7 by 150%, which is 10.5', so B = 10.5". The percent of change is 50%. I am afraid I don't understand the string of numbers below the initial problem. Do you need the percent of change for these? If so, just set them up in algebra, thus: (x%)60 = 36; x% = 36/60; x = 60%, so 36 is 60% of 60. Conversely, 60 = x%(36); 60/36=x%; x=166.67%, so 60 is 166.67% of 36.

Answer 3

The equation for 1 is 5/7 = 7.5/B cross multiply to get B.

The others: first find the actual change then write this proportion:

(change)/(original amount) = x/100

Again cross multiply to solve.

Like your first the change was 60-36 = 24

So 24/60 = x/100
2400 = 60x

40 = x; a 40% decrease

Answer 4

just use fractions for 1st question:
5/7 = 7.5/B
cross multiply to 5B=52.5
B=10.5

2nd question
divide 36 w/ 60 so its 0.6 which means it dropped 60%
18 to 24 increased about 133%
85 to 50 dropped 58%
8.8 to 30 increased about 340%
1.2 to 0.2 decreased about 16%

Answer 5

well, it was
5/7, now it's B/7.5

mulitply 5 by 7.5, and 7 by B.

so 37.5 = 7B

now divide 37.5 by 7 to get your answer.

Answer 6

5 7.5
-- = ------
7 B

So B = (7)(7.5)/5

the percentage change would be 7.5/5*100

Answer 7

use a proportion.

or cross multiply and divide.


for percent: divide

Answer 8

This is easy stuff, and I think you need to do your own homework! What is our society coming to? We are going to have lazy morons running the future! God help us all!