Irene was saving money to buy pens. She saved $3 every 5 days. After saving for 65 days, she went to buy pens that were on sale.

1. What was the most number of pens she could buy?
2. Irene wanted to buy 34 pens. How much more did she need to save?

(a)
Number of sets of 5 days
= 65 ÷ 5
= 13

Amount that Irene saved in 65 days
= 13 x 3
= $39

Maximum number of sets of 5 pens that Irene could buy 
= 39 ÷ 8
= 4 r $7

Remaining amount left after buying sets of 5 pens = $7

Maximum number of sets of 3 pens that Irene could buy with $7
= 7 ÷ 5
= 1 r $2 

Remaining amount left after buying sets of 3 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 5 + 1 x 3 + 1
= 20 + 3 + 1
= 24

(b)
Number of sets of 5 pens that Irene could buy
= 34 ÷ 5
= 6 r 4

Number of sets of 3 pens that Irene could buy
= 4 ÷ 3
= 1 r 1

Number of individual pens that Irene could buy = 1

Amount that Irene needed to buy 34 pens
= 6 x 8 + 1 x 5 + 2
= 48 + 5 + 2
= $55

Amount that Irene needed to save more
= 55 - 39
= $16

Answer(s): (a) 24; (b) $16