Gabby was saving money to buy pens. She saved $9 every 6 days. After saving for 36 days, she went to buy pens that were on sale.

1. What was the most number of pens she could buy?
2. Gabby wanted to buy 54 pens. How much more did she need to save?

(a)
Number of sets of 6 days
= 36 ÷ 6
= 6

Amount that Gabby saved in 36 days
= 6 x 9
= $54

Maximum number of sets of 8 pens that Gabby could buy 
= 54 ÷ 11
= 4 r $10

Remaining amount left after buying sets of 8 pens = $10

Maximum number of sets of 5 pens that Gabby could buy with $10
= 10 ÷ 7
= 1 r $3 

Remaining amount left after buying sets of 5 pens = $3

Maximum number of pens that Gabby could buy with $3 
= 3 ÷ 3
= 1

Most number of pens that Gabby could buy
= 4 x 8 + 1 x 5 + 1
= 32 + 5 + 1
= 38

(b)
Number of sets of 8 pens that Gabby could buy
= 54 ÷ 8
= 6 r 6

Number of sets of 5 pens that Gabby could buy
= 6 ÷ 5
= 1 r 1

Number of individual pens that Gabby could buy = 1

Amount that Gabby needed to buy 54 pens
= 6 x 11 + 1 x 7 + 3
= 66 + 7 + 3
= $76

Amount that Gabby needed to save more
= 76 - 54
= $22

Answer(s): (a) 38; (b) $22