The average height of some boys is 144 cm. When 3 girls, with a total height of 405 cm, are included, the average height if the children becomes 141 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
144 |
|
141 |
Total value |
144 u |
405 |
141 u + 423 |
Total height of the boys
= 1 u x 144
= 144 u
Total height of the children = 144 u + 405
144 u + 405 = 141 u + 423
144 u - 141 u = 423 - 405
3 u = 18
1 u = 18 ÷ 3 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9