The average height of some boys is 146 cm. When 3 girls, with a total height of 390 cm, are included, the average height if the children becomes 142 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
146 |
|
142 |
Total value |
146 u |
390 |
142 u + 426 |
Total height of the boys
= 1 u x 146
= 146 u
Total height of the children = 146 u + 390
146 u + 390 = 142 u + 426
146 u - 142 u = 426 - 390
4 u = 36
1 u = 36 ÷ 4 = 9
Total number of children
= 1 u + 3
= 9 + 3
= 12
Answer(s): 12