Question

Ques 18) A bag contains Rs 600 in notes of denominations of Rs 10 and Rs 3
20. If the number of Rs 20 notes is twice the number of Rs 10 notes, then
find the number of Rs 20 notes.​

Answer 1

Solution-

Let the number of ₹ 10 notes be x.

So, number of ₹ 20 notes = 2x.

∴ Total amount of ₹ 10 notes = ₹ 10x

∴ Total amount of ₹ 20 notes = ₹ (20×2x)

Total amount in the bag = ₹ 600

According to condition,

10x + (20×2x) = 600

or, 10x + 40x = 600

or, 50x = 600

or, x = 600/50

or, x = 12

So, number of ₹ 10 notes = x = 12

and number of ₹ 20 notes = 2x = 2×12 = 24

Hence, the number of ₹ 20 notes is 24.

Verify-

₹ 10x + ₹ (20×2x) = ₹ 600

or,  ₹ 10x + ₹ 40x = ₹ 600

or, ₹ (10×12) + ₹ (40×12) = ₹ 600

or, ₹ 120 + ₹ 480 = ₹ 600

or, ₹ (120 + 480) = ₹ 600

or, ₹ 600 = ₹ 600

Hence, L.H.S = R.H.S.