Level 3
The average height of some boys is 145 cm. When 3 girls, with a total height of 393 cm, are included, the average height if the children becomes 142 cm. How many children are there altogether?
Level 3
Simon has some black and red balls. The total mass of all his balls is 242 g. He has 5 more red balls than black balls. The average mass of the black balls is 6 g. The average mass of the red balls is 10 g. How many balls does Simon have altogether?
Level 3
Shiyun, Kimberly and Yoko had jelly beans in the ratio of 8 : 4 : 3. After Shiyun gave 6 jelly beans to Kimberly and Yoko, the three of them had the same number of jelly beans. Find the total number of jelly beans the children had.