The average height of some boys is 131 cm. When 3 girls, with a total height of 321 cm, are included, the average height if the children becomes 123 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
131 |
|
123 |
Total value |
131 u |
321 |
123 u + 369 |
Total height of the boys
= 1 u x 131
= 131 u
Total height of the children = 131 u + 321
131 u + 321 = 123 u + 369
131 u - 123 u = 369 - 321
8 u = 48
1 u = 48 ÷ 8 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9