Level 3
A briefcase with 5 magazines in it has a mass of 2.58 kg. When 6 more magazines and 22 guide books are added, the mass becomes 4.28 kg. Each magazine has a mass 2 times as much as each guide book. Find the mass of the briefcase when it is empty. Express the answer in kg.

Level 3
Three cartons, A, B and C, contained 382 marbles. Hazel added some marbles into Carton A and the number of marbles in Carton A tripled. He took out half of the number of marbles from Carton B and added another 98 marbles into Carton C. As a result, the ratio of the number of marbles in Carton A, Carton B and Carton C became 6 : 2 : 9. What was the ratio of the number of marbles in Carton B to the total number of marbles in Carton A and Carton C at first? Give the answer in its lowest term.

Level 3
At a fun fair, there were 3 times as many males as females. ⁵₉ of the males were boys and the rest were men. ²₃ of the females were women and the rest were girls. Given that there were 104 more boys than girls, how many children were there altogether?

Level 3
Betty spent ⁴₅ of her money on 14 stamps and 5 pens. The cost of each pen is 2 times the cost of each stamp. She bought some more stamps with ²₃ of her remaining money. How many stamps did Betty buy altogether?

Level 3
Carl had a total of 90 notes. The notes are $10 notes and $5 notes. After he spent 20% of the $10 notes and 60% of the $5 notes on a stereo system, he was left with 4 times as many $5 notes as $10 notes. How much did the stereo system cost?