A bag has Rs12.9 in the form of 1 rupee, 50 paise and 10 paise coins in the ratio of 3:2:3. How many 50 paise coins are there in the bag?

Let the number of 1-rupee, 50-paise and 10-paise coins be $$3x$$ , $$2x$$ and $$3x$$ respectively.

Total amount in the bag = Rs. 12.9

=> $$(1 \times 3x) + (\frac{50}{100} \times 2x) + (\frac{10}{100} \times 3x) = 12.9$$

=> $$3x + x + \frac{3x}{10} = 12.9$$

=> $$\frac{30x + 10x + 3x}{10} = 12.9$$

=> $$43x = 12.9 \times 10 = 129$$

=> $$x = \frac{129}{43} = 3$$

$$\therefore$$ Number of 50 paise coins = $$2x = 2 \times 3 = 6$$

=> Ans - (B)