Amanda A. answered • 03/26/14

Experienced Teacher and Education Professional w/ Test-Prep Experience

**25/60 = s/12**

**25/60 = (5*s)/(5*12)**

**25/60 = 5s/60**

**25/60 * 60 = 5s/60 * 60**

**25/60 * 60 = 5s/60 * 60**

**25 = 5s**

**25 = 5s**

**25/5 = 5s/5**

**5 = 5s/5**

**5 = s**

Brianna H.

asked • 03/26/14I really need homework help on solving proportions(glencoe -pre algebra) 8th grade

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Amanda A. answered • 03/26/14

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There are two ways that we can solve this problem! The first is to treat the proportions like fractions (which they are) and try to convert one of the fractions so that it has the same value, but has the same denominator as the other fraction. Luckily, 12 fits perfectly 5 times into 60!

From here, we have two different numbers both being divided by 60. We can multiply both sides by 60 to simplify.

Finally, to solve for the variable (s), we need to get it by itself or "isolate" it. We can do that here by dividing both sides by 5!

There's our answer! s=5! I hope this was helpful, Brianna!

Parviz F. answered • 03/26/14

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Mathematics professor at Community Colleges

a/ b = c/d (1)

Multiply both sides by bd

bd( a/b) = bd( c/d)

dividing both sides bd

ad = bc

Cross multiplication is multiplying both sides of the equation by product of the denominators, and diving by the same term you see from the above equations equality of cross multiplication is obtained.

So

if :

2/3 = X/ 7

Now we multiply both sides by 21= 3(7)

21( 2/3) = 21 ( X/7)

7 (2) = 3X

X = 14/3

Can look at this this way too

2/ 3 = 2(4) /3( 4)

/ we can multiply numerator and denominator and maintain the equality of the fraction .

By the same line of reasoning:

2/3 = X/ 12 (3)

if we have 2 fractions equal ( 3).

12 = 3(4)

8 has to be product of 2 by 4 equals 8.

Keith M. answered • 03/26/14

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Keith - Tutoring mathematics from middle up to college mathematics

Hi Brianna

Cross multiply to get what the value of s is to solve the proportion.

25*12=60*s

So 300 = 60s

Divide each side by 60 to isolate s.

Therefore s = 5.

Substitute 5 in for s to check your answer.

5/12 = 25/60

We notice that 5 *5 = 25

We notice 12 * 5 = 60

Thus our solution, s = 5, is correct.

Keith Messmer

Diane S. answered • 03/26/14

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Math and Chemistry Tutor. Test Prep: SAT/ACT, Praxis, ISEE and more!

Many students like cross multiplication for problems like this. Write the fractions vertically, each with a top and a bottom. Draw a big X through the problem. This X will connect the 25 to the 12 and the 60 to the s.

The equation is then rewritten as

(25)(12) = (60)(s)

now divide both sides by 60 to get the variable you are solving for, s, alone:

(25)(12)/(60) = s

at this point, most students reach for their calculator. But I always ask students to look first if the problem can be reduced - many times it can be, and a calculator is not even necessary.

In this case the left side of the problem reduces to 25/5 = 5.

In fact, in the original problem, the 25/60 reduces by dividing a 5 out of both the top and bottom. This leads directly to an answer since 25/60 = (5x5)/(5x12) = 5/12. Comparing 5/12 to s/12 shows s=5.

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