Oliver, Liam and Billy had 272 pens. After Oliver used 31 pens and Liam used
37 of her pens, Oliver had thrice as many pens left as Liam. Billy bought another 39 pens, he had four times the number of pens Liam had left. How many pens did Billy have at first?
| |
Oliver |
Liam |
Billy |
Total |
| Before |
12 u + 31 |
7 u |
16 u - 39 |
272 |
| Change |
- 31 |
- 3 u |
+ 39 |
|
| After |
12 u |
4 u |
16 u |
|
Comparing Oliver
and Liam in the end |
3 |
1 |
|
|
Comparing Billy
and Liam in the end |
|
1 |
4 |
|
Number of pens that Oliver had in the end
= 3 x 4 u
= 12 u
Number of pens that Billy had in the end
= 4 x 4 u
= 16 u
Total number of pens at first
= 12 u + 31 + 7 u + 16 u - 39
= 35 u - 8
35 u - 8 = 272
35 u = 272 + 8
35 u = 280
1 u = 280 ÷ 35 = 8
Number of pens that Billy had at first
= 16 u - 39
= 16 x 8 - 39
= 128 - 39
= 89
Answer(s): 89
