f.1 maths

1. One number is 4 times that of another number. Their sum is 45. What are the numbers?
Let be the number x,
4x + x = 45
5x = 45
x = 9
Therefore the number is 9 and 36 (45-9).
2. In a test, Peter gets 2 marks for each correct sum and loses 1 mark for each wrong sum. He does 18 sums and obtains 24marks. How many correct sums does he get?
Let correct sums be x, wrong sum be (18 - x):
2x + (18 - x)1 = 24
2x + 18-x = 24
x = 6
Therefore he get 6 correct sum.
3. boy divides 60 marbles into 2 groups so that 7 times the smaller group is equal to 3 times the larger group. What is the number of marbles in the larger group?
Let be the number of marbles in the smaller group is 7x, larger group is 3x:
60 - 7x = 3x
60 = 10x
x = 6
Therefore the larger group have 18 marbles.

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