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# Maths worksheets for challenging problem sums

Related Skills
Skill Involving Changing quantities
Ratio
Fraction

## * Practice for skill involving changing quantities

1) In a library, the ratio of the number of boys to the number of girls was 6:5. ½ of the boys and 25 of the girls left the library. 20 pupils stayed behind. How many pupils were in the library at first?

Ans :- 28 pupils.

2) Last year the ratio of the number of boys to the number of girls in the computer club was 2:5. This year 81 new members joined the club and there are now 3 times as many boys and 2 times as many girls as last year. How many members were there in the club last year?

Ans :- 30 members.

3) Mr. Li's salary in January was \$2 400. He saved ½ of the salary. In February, his salary was increased by 5%, but his expenditure went up by 10%. How much money did he save in February?

Ans :- \$1200.

4) In a class library, 60% of the books were story books and the rest were science books. When 80 new books were added to the library, the number of story books was doubled and the number of science books was increased by 50%. How many books were there in the library at first?

Ans :- 100 books.

5) A school library had 1600 books. These were Chinese, Malay and English books in the ratio 5:3:8. When the librarian bought 160 new books, the number of Chinese books was increased by 12% and the number of Malay books was increased by 20% by what percentage was the number of English books increased?

Ans :- 5 %.

6) Aihua has 20% more beads than Meimei. If Aihua gives 30 beads to Meimei, Meimei will have 20% more beads than Aihua. How many beads do they have altogether?

Ans :- 330 beads.

7) The ratio of the number of shells to the number of beads Linda had was 1:3. When she collected 15 more shells and 120 more beads, 15 of the total collection of shells and beads were made up of shells. How many shells did Linda have at first?

Ans :- 60 shells.

8) Mr. Lim spends \$840 of his monthly salary and saves the rest. If his monthly expenses are decreased by \$120, his monthly savings will be increased by 20%. Find his monthly salary.

Ans :- \$1440.