Erika was saving money to buy pens. She saved $5 every 3 days. After saving for 21 days, she went to buy pens that were on sale.
- What was the most number of pens she could buy?
- Erika wanted to buy 33 pens. How much more did she need to save?
(a)
Number of sets of 3 days
= 21 ÷ 3
= 7
Amount that Erika saved in 21 days
= 7 x 5
= $35
Maximum number of sets of 7 pens that Erika could buy
= 35 ÷ 9
= 3 r $8
Remaining amount left after buying sets of 7 pens = $8
Maximum number of sets of 4 pens that Erika could buy with $8
= 8 ÷ 6
= 1 r $2
Remaining amount left after buying sets of 4 pens = $2
Maximum number of pens that Erika could buy with $2
= 2 ÷ 2
= 1
Most number of pens that Erika could buy
= 3 x 7 + 1 x 4 + 1
= 21 + 4 + 1
= 26
(b)
Number of sets of 7 pens that Erika could buy
= 33 ÷ 7
= 4 r 5
Number of sets of 4 pens that Erika could buy
= 5 ÷ 4
= 1 r 1
Number of individual pens that Erika could buy = 1
Amount that Erika needed to buy 33 pens
= 4 x 9 + 1 x 6 + 2
= 36 + 6 + 2
= $44
Amount that Erika needed to save more
= 44 - 35
= $9
Answer(s): (a) 26; (b) $9
