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how to set up proportions?

for example ''Mrs. Stearns need to photocopy a 9.5 cm wide by 16 cm long picture. She wants to enlarge the picture so its length is 40 cm. How wide will the picture be?'' i need help on these kind of problems i will be getting a tutor soon so watch out. and please help me online with my homework because i might get kicked out of my upper level [above grade level] math class so please help me! i greatly appreciate all your help!!!

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2 Answers

Proportions are ratios. A ratio is simply one dimension divided by another. Example is Width/Length. Mrs. Stearns most likely wishes the Width/Length ratio for her new photocopy to stay the same as old one. 1) Width (old)/Length (old)= Width (new)/Length (new)...this is the form of the calculation to be made. 2) We know Width (old) = 9.5cm, Length (old)= 16cm, Length (new) = 40cm as givens. 3) We want to calculate Width (new) so rearrange 1) as below: 4) Width(old)/Length(old)*Length(new)=Width(new) 5) Width(new)= 9.5/16*40= 23.75 cm


thanks so much u really explain well!!! i greatly appreciate all your help. I hope you Get what U deserve in Life because u are a great person.


I would set up the problem so that the current dimensions become fractions:

9.5 cm wide/16 cm long; or 9.5/16

Compare that to the desired dimensions of:

x (unknown)/ 40 cm long; or x/40

Then Cross Multiply:

40 * (times) 9.5 = you got this!

16 * (times) x (or the unknown number)= 16x

The last step is to divide the two products:

you got this/16x

What you get is the unknown, or x. That's how wide it would be!