Ｈｅｌｐ

Well, when the jar goes from 1/4 to 1/3 it is 30 pennies:

 

1/3 - 1/4 = 30

4/12 -3/12 = 1/12 = 30 pennies

 

 

3/4 full = 9/12      1/12 is 30    then 9/12 is NINE TIMES MORE or  9x30= 270 pennies

Michael has a jar of pennies that is 1/4 full. When he adds 30 pennies, the jar becomes 1/3 full. When Michael's jar of pennies is 3/4 full, how many pennies will it contain?

 

Let the number P=pennies when the Jar is 1/4 full. But we have:

1/4P + 30=1/3P

1/3P - 1/4P=30

1/12P=30 multiply both sides by 12

P=360 pennies when the jar is 1/4 full, but since 3/4 is 3 times 1/4, therefore,

360 X 3=1,080 pennie when the jar 3/4 full.

A slight mistake in guest#2  answer.

 

He/she should have said P =pennies when jar is FULL  (not 1/4 full)

then

1/4P + 30 = 1/3P

1/3P - 1/4P = 30

1/12P = 30

Multiply both sides by 12

P=Full jar=360

 

We want to know how many pennies when 3/4 full

 

3/4 P =  3/4 (360) = 270 when 3/4 full.