Question

A jar of pennies was 1/4 full. David put 25 pennies in, and now it is 1/3 full. How many pennies will be in the jar when it is 3/4 full?

Answer 1

225 pennies will be in the jar once 3/4 full.

Explanation:

First you want to find what fraction was added to 1/4 to get 1/3 to find what that fraction of the jar equals 25. To do this you want to subtract 1/4 from 1/3. 1/3-1/4= 1/12. 1/12 of the jar is equal to 25 pennies.

Next you can set the problem up as a ratio to help solve the problem. 1/12:25 means for every 12th of the jar, 25 pennies are added. Next you need to multiply on both sides by 9 because you would get the ratio 9/12:225. 9/12 can be simplified to 3/4 which makes the new ratio into 3/4:225

Answer 2

Answer:125 pennies

Explanation:

First we will have to look at the increase in volume, the jar was originally 1/4 but when 25 coins was put in it, it rises to 1/3.

So increase in volume is 1/3 - 1/4 = 1/12

so when 25 coins were inserted in the jar the volume increase by 1/12

Now, to the second part of the question, when x coin was put into the jar, the volume rise from 1/3 to 3/4, we will also find the rise in volume; 3/4 - 1/3 = 5/12

We can now solve using proportion;

25 pennies = 1/12

x pennies = 5/12

cross multiply

25 × 5/12 = 1/12 X

multiply bothside by 12 to make x stand alone.

25 × 5 = X

125 = X

X = 125

Therefore 125 pennies will be needed in the jar when it is 3/4 full