The average height of some boys is 150 cm. When 3 girls, with a total height of 390 cm, are included, the average height if the children becomes 144 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
150 |
|
144 |
Total value |
150 u |
390 |
144 u + 432 |
Total height of the boys
= 1 u x 150
= 150 u
Total height of the children = 150 u + 390
150 u + 390 = 144 u + 432
150 u - 144 u = 432 - 390
6 u = 42
1 u = 42 ÷ 6 = 7
Total number of children
= 1 u + 3
= 7 + 3
= 10
Answer(s): 10