The average height of some boys is 138 cm. When 3 girls, with a total height of 378 cm, are included, the average height if the children becomes 134 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
138 |
|
134 |
Total value |
138 u |
378 |
134 u + 402 |
Total height of the boys
= 1 u x 138
= 138 u
Total height of the children = 138 u + 378
138 u + 378 = 134 u + 402
138 u - 134 u = 402 - 378
4 u = 24
1 u = 24 ÷ 4 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9