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
Kylie bought some Geography books at $17 each. She also bought an equal number of History books at a different price. The average price of one Geography and one History book was $10. Kylie paid $70 more for the Geography books than the History books.
Level 3
The average mass of a group of girls is 45 kg. If one more girl who weighs 75 kg joins the group, the new average mass of the group will become 48 kg. Find the total number of girls in the group.
Level 3
The average number of pages Joan read in a certain number of days was 15. In the next four days, Joan read another 88 pages. As a result, the average number of pages she read increased to 17. How many days did Joan read in total?
