Unitary Method
 If 20 articles cost ₹ 90, then the cost of 9 articles is ?

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Cost of 20 articles = ₹ 90
Cost of 1 article = ₹ 90/20
Correct Option: B
Cost of 20 articles = ₹ 90
Cost of 1 article = ₹ 90/20
∴ Cost of 9 article = 9 x 90/20 = ₹ 40.50
 If cost of 24 oranges is ₹ 72, then find out the cost of 120 oranges.

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Let the required cost be ₹ N.
More orange, more cost (Direct proportion)
24 : 120 : : 72 : NCorrect Option: B
Let the required cost be ₹ N.
More orange, more cost (Direct proportion)
24 : 120 : : 72 : N
∴ N = (120 x 72)/24 = ₹ 360
 If cost of 12 pens is ₹ 84, then what is the cost of 10 such pens ?

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∵ Cost of 12 pens = ₹ 84
Cost of 1 pen = ₹ 84/12Correct Option: D
∵ Cost of 12 pens = ₹ 84
Cost of 1 pen = ₹ 84/12
∴ Cost of 10 pens = (84/12) x 10
= 7 x 10 = ₹ 70
 If cost of 15 eggs is ₹ 75, then find out the cost of 4 dozens eggs.

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∵ Cost of 15 eggs = ₹ 75
∴ Cost of 1 egg = ₹ 75/15
∴ Cost of 4 dozens (4 x 12) = Cost of 48 eggsCorrect Option: A
∵ Cost of 15 eggs = ₹ 75
∴ Cost of 1 egg = ₹ 75/15
∴ Cost of 4 dozens (4 x 12) = Cost of 48 eggs
= (75/15) x 48 = ₹ 240
 If 16 dozens bananas cost ₹ 360, then how many bananas can be bought in ₹ 60 ?

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Let the required number of bananas be N.
16 dozens bananas = 16 x 12 = 192 bananas
Less bananas, Less cost (Direct proportion)
360 : 60 : : 192 : NCorrect Option: C
Let the required number of bananas be N.
16 dozens bananas = 16 x 12 = 192 bananas
Less bananas, Less cost (Direct proportion)
360 : 60 : : 192 : N
∴ N = (60 x 192)/360 = 32 bananas