George, Rael and Daniel had 72 pencils. After George used 17 pencils and Rael used
14 of her pencils, George had twice as many pencils left as Rael. Daniel bought another 21 pencils, he had thrice the number of pencils Rael had left. How many pencils did Daniel have at first?
| |
George |
Rael |
Daniel |
Total |
| Before |
6 u + 17 |
4 u |
9 u - 21 |
72 |
| Change |
- 17 |
- 1 u |
+ 21 |
|
| After |
6 u |
3 u |
9 u |
|
Comparing George
and Rael in the end |
2 |
1 |
|
|
Comparing Daniel
and Rael in the end |
|
1 |
3 |
|
Number of pencils that George had in the end
= 2 x 3 u
= 6 u
Number of pencils that Daniel had in the end
= 3 x 3 u
= 9 u
Total number of pencils at first
= 6 u + 17 + 4 u + 9 u - 21
= 19 u - 4
19 u - 4 = 72
19 u = 72 + 4
19 u = 76
1 u = 76 ÷ 19 = 4
Number of pencils that Daniel had at first
= 9 u - 21
= 9 x 4 - 21
= 36 - 21
= 15
Answer(s): 15
