Shiyun had a total of 209 grey and black balls. She used
45 of her grey balls and bought another 64 black balls. The number of black balls she had then become
14 the number of grey balls. How many less black balls than grey balls did she have at first?
| |
Grey balls |
Black balls |
| Before |
5x4 |
|
| Change |
- 4x4 |
+ 64 |
| After |
1x4 |
|
| Comparing balls in the end |
4x1 |
1x1 |
| |
Grey balls |
Black balls |
| Before |
20 u |
1 u - 64 |
| Change |
- 16 u |
+ 64 |
| After |
4 u |
1 u |
The number of grey balls in the end is repeated.
LCM of 1 and 4 is 4.
Total number of grey balls and black balls
= 20 u + 1 u - 64
= 21 u - 64
21 u - 64 = 209
21 u = 209 + 64
21 u = 273
1 u = 273 ÷ 21 = 13
Number of less black balls than grey balls at first
= 20 u - (1 u - 64)
= 19 u + 64
= 19 x 13 + 64
= 311
Answer(s): 311
