Ex 2.2, 15 I have a total of Rs 300 in coins of denomination Re 1, Rs 2 and Rs 5. The number of Rs 2 coins is 3 times the number of Rs 5 coins. The total number of coins is 160. How many coins of each denomination are with me?Let Number of Rs 5 coin = x
Given number of Rs 2 coins is 3 times number of Rs 5 coins
∴ Number of Rs 2 coins = 3x
Also, given that
Total number of coins = 160
No. of Rs 5 coins + No. of Rs 2 coins + No. of Rs 1 coin = 160
x + 3x + Number of Rs 1 coin = 160
4x + Number of Rs 1 coin = 160
Number of Rs 1 coin = 160 − 4x
Given,
Total amount = Rs 300
160 − 4x + 6x + 5x = 300
160 − 4x + 11x = 300
160 + 7x = 300
7x = 300 − 160
7x = 140
Rough
If I have one 5 Rs coin, then Amount = 1 × 5 = 5
If I have 2 Rs 5 coins, then Amount = 2 × 5 = 10
If I have 3 Rs 5 coins, then Amount = 3 × 5 = 15
x = 140/7
x = 20
Therefore,
Number of 5 Rs coins = x = 20
Number of 2 Rs coins = 3x = 3 × 20 = 60
Number of Re 1 coins = 160 − 4x = 160 − 4 × 20 = 160 − 80 = 80

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.