Adding and subtracting fractions (stories)

Advanced Math 5 · Unit 7 · fraction-add-sub-5 · Teacher edition

fraction-add-sub-5

Name ______________________________Date ______________

1.
Compute $3\dfrac{1}{4} - 1\dfrac{2}{3}$ . Give your answer as a fraction or mixed number.
Answer: ______________
2.
Mia has a ribbon $60$ cm long. She uses $\dfrac{1}{4}$ of it for a bow, then $\dfrac{2}{3}$ of the remainder for a bookmark. How many centimetres of ribbon are left?
Answer: ______________
3.
Jo had $40$ beads. She gave $\dfrac{2}{5}$ of them to Ali, then $\dfrac{1}{4}$ of the remainder to Bea. How many beads does Jo have left?
1. (A)
  $6$
2. (B)
  $14$
3. (C)
  $24$
4. (D)
  $18$

Answer key — Adding and subtracting fractions (stories)

1.
19/12fraction-add-sub-5-01
$3\frac{3}{12} - 1\frac{8}{12} = 2\frac{15}{12} - 1\frac{8}{12} = \mathbf{1\tfrac{7}{12}}$ . (As improper fractions: $\frac{39}{12} - \frac{20}{12} = \frac{19}{12}$ .)
2.
15fraction-add-sub-5-02
Bow: $\frac{1}{4} \times 60 = 15$ cm, leaving $45$ cm. Bookmark: $\frac{2}{3} \times 45 = 30$ cm. Left: $45 - 30 = \mathbf{15}$ cm. (In fractions of the whole: $\frac{3}{4}$ remains after the bow, the bookmark is $\frac{2}{3}$ of $\frac{3}{4} = \frac{1}{2}$ , and $\frac{1}{4}$ of $60$ is left.)
3.
(D)
$18$
fraction-add-sub-5-03
Ali: $\frac{2}{5} \times 40 = 16$ , leaving $24$ . Bea: $\frac{1}{4} \times 24 = 6$ . Jo keeps $24 - 6 = \mathbf{18}$ . ( $14$ takes $\frac{1}{4}$ of the original $40$ instead of the remainder; $24$ forgets Bea; $6$ is Bea's share.)