The average height of some girls is 138 cm. When 3 boys, with a total height of 354 cm, are included, the average height if the children becomes 133 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
138 |
|
133 |
Total value |
138 u |
354 |
133 u + 399 |
Total height of the girls
= 1 u x 138
= 138 u
Total height of the children = 138 u + 354
138 u + 354 = 133 u + 399
138 u - 133 u = 399 - 354
5 u = 45
1 u = 45 ÷ 5 = 9
Total number of children
= 1 u + 3
= 9 + 3
= 12
Answer(s): 12