Irene was saving money to buy pens. She saved $4 every 3 days. After saving for 36 days, she went to buy pens that were on sale.
- What was the most number of pens she could buy?
- Irene wanted to buy 59 pens. How much more did she need to save?
(a)
Number of sets of 3 days
= 36 ÷ 3
= 12
Amount that Irene saved in 36 days
= 12 x 4
= $48
Maximum number of sets of 9 pens that Irene could buy
= 48 ÷ 10
= 4 r $8
Remaining amount left after buying sets of 9 pens = $8
Maximum number of sets of 5 pens that Irene could buy with $8
= 8 ÷ 6
= 1 r $2
Remaining amount left after buying sets of 5 pens = $2
Maximum number of pens that Irene could buy with $2
= 2 ÷ 2
= 1
Most number of pens that Irene could buy
= 4 x 9 + 1 x 5 + 1
= 36 + 5 + 1
= 42
(b)
Number of sets of 9 pens that Irene could buy
= 59 ÷ 9
= 6 r 5
Number of sets of 5 pens that Irene could buy
= 5 ÷ 5
= 1 r 0
Amount that Irene needed to buy 59 pens
= 6 x 10 + 1 x 6
= 60 + 6
= $66
Amount that Irene needed to save more
= 66 - 48
= $18
Answer(s): (a) 42; (b) $18
