Fractional Parts

If you spend one-fourth of a dollar, how much is left?

First divide the dollar into four equal pieces (the denominator -- bottom number -- tells how many equal pieces are in each whole thing). 100 ÷ 4 = 25. That's the amount used.   What was the question?   How much of the dollar is left?

You can set-up and solve this type of question as a proportion:

3 out of 4 equals how much out of 100 -- 3 times 100 divided by 4

Use cross-products to solve: 3 times 100 = 4 times (the missing part)

3 times 100 = 4 times the amount left
300 = 4 times the amount left
300/4 = 4/4 times the amount left
75 (cents) =   the amount left

Notice that the answer will be for whatever question you asked --the set-up can save you an extra step later (or save you from forgetting that there was a second step).

You fold one-third of sixty napkins.   How many are left?

all 3/3 of the napkins minus 1/3 (already folded) shows that two-thirds of them left.

two-thirds of the 60 napkins are left to be folded.  2 times 60 divided by 3 equals 40 napkins left.

Jack's rent is two-fifths of his income.   If he earns $1500, how much is his rent?

Jack earns $1500 and pays two-fifths of it for rent.  2 times 1500 divided by 5 equals &600 rent.


1)   Tom broke one-sixth of a dozen eggs. How many eggs are not broken?
2)   Kim ate one-fourth of sixty mints.   How many mints are left?
3)   Pam painted three-fourths of the tiles.   How many of the 80 tiles are painted?
4)   Dale sold one-eighth of the books.   How many of the 40 books are left?


1)   10 eggs are UNBROKEN     2)   45 are left     3)   60 are painted     4)   35 are left

Amby's Math Instruction, Reinforcement, and Learning Activities
Math Education Resources
Math Puzzles & Learning Activities

Brain Games
Cat Site
Test Prep
Work Site

© 1999 Amby Duncan-Carr   All rights reserved.

The URL of this page is: