Ken, Cody and Justin had 84 pencils. After Ken used 4 pencils and Cody used
35 of her pencils, Ken had thrice as many pencils left as Cody. Justin bought another 10 pencils, he had twice the number of pencils Cody had left. How many pencils did Justin have at first?
| |
Ken |
Cody |
Justin |
Total |
| Before |
6 u + 4 |
5 u |
4 u - 10 |
84 |
| Change |
- 4 |
- 3 u |
+ 10 |
|
| After |
6 u |
2 u |
4 u |
|
Comparing Ken
and Cody in the end |
3 |
1 |
|
|
Comparing Justin
and Cody in the end |
|
1 |
2 |
|
Number of pencils that Ken had in the end
= 3 x 2 u
= 6 u
Number of pencils that Justin had in the end
= 2 x 2 u
= 4 u
Total number of pencils at first
= 6 u + 4 + 5 u + 4 u - 10
= 15 u - 6
15 u - 6 = 84
15 u = 84 + 6
15 u = 90
1 u = 90 ÷ 15 = 6
Number of pencils that Justin had at first
= 4 u - 10
= 4 x 6 - 10
= 24 - 10
= 14
Answer(s): 14
