The average height of some boys is 150 cm. When 3 girls, with a total height of 387 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 |
150 |
|
141 |
Total value |
150 u |
387 |
141 u + 423 |
Total height of the boys
= 1 u x 150
= 150 u
Total height of the children = 150 u + 387
150 u + 387 = 141 u + 423
150 u - 141 u = 423 - 387
9 u = 36
1 u = 36 ÷ 9 = 4
Total number of children
= 1 u + 3
= 4 + 3
= 7
Answer(s): 7