There were some marbles in a box. Sofie took out 2/5 of the marbles and put in 6 more. Then John took out 1/6 of the remaining marbles and put in 5 more. there were 25 marbles left. How many marbles were in the box at first?
Solution
6 units - 1 unit + 6 - 1 + 5 --> 25 (left in box)
5 units + 10 --> 25
5 units --> 25 - 10 = 15
1 unit --> 15 divided by 5 = 3
Marbles at first
--> 10 units x 3
= 30
(At first, there were 10 units and not 5 units because the 5 units have been cut into halves, giving a total of 10 smaller units)
Answer: 30 marbles
Wednesday, February 17, 2010
Nanyang Pri Sch 2009 P6 CA1 Math Paper 2 Q11
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