Abi was saving money to buy pens. She saved $3 every 4 days. After saving for 40 days, she went to buy pens that were on sale.
- What was the most number of pens she could buy?
- Abi wanted to buy 31 pens. How much more did she need to save?
(a)
Number of sets of 4 days
= 40 ÷ 4
= 10
Amount that Abi saved in 40 days
= 10 x 3
= $30
Maximum number of sets of 7 pens that Abi could buy
= 30 ÷ 8
= 3 r $6
Remaining amount left after buying sets of 7 pens = $6
Maximum number of sets of 3 pens that Abi could buy with $6
= 6 ÷ 4
= 1 r $2
Remaining amount left after buying sets of 3 pens = $2
Maximum number of pens that Abi could buy with $2
= 2 ÷ 2
= 1
Most number of pens that Abi could buy
= 3 x 7 + 1 x 3 + 1
= 21 + 3 + 1
= 25
(b)
Number of sets of 7 pens that Abi could buy
= 31 ÷ 7
= 4 r 3
Number of sets of 3 pens that Abi could buy
= 3 ÷ 3
= 1 r 0
Amount that Abi needed to buy 31 pens
= 4 x 8 + 1 x 4
= 32 + 4
= $36
Amount that Abi needed to save more
= 36 - 30
= $6
Answer(s): (a) 25; (b) $6
