Multiple choice

A person invested some amount at the rate of 12% simple interest and the remaining at 10%. He received yearly an interest of Rs. 130. Had he interchanged the amounts invested, he would have received an yearly interest of Rs. 134. How much money did he invest at different rates? एक व्यक्ति ने कुछ राशि 12% की दर से साधारण ब्याज पर और शेष राशि 10% पर निवेश किया । उसे सालाना 130 रूपये का ब्याज मिला। यदि उसने निवेश की गई राशियों को अदला - बदली कर दी होती तो उसे 134 रूपये का सालाना ब्याज प्राप्त होता। उसने भिन्न दरों पर कितनी राशि निवेश की?

  1. Rs.500 @ 10%, Rs.800 @ 12%

  2. Rs.700 @ 10%, Rs.600 @ 12%

  3. Rs.800 @ 10%, Rs.400 @ 12%

  4. Rs.700 @ 10%, Rs.500 @ 12%

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let amount at 12% = x and at 10% = y. Then 0.12x + 0.10y = 130 and 0.10x + 0.12y = 134. Subtracting: -0.02x + 0.02y = 4, so y - x = 200. From first eq: 12x + 10(x + 200) = 13000 gives 22x + 2000 = 13000, so 22x = 11000, x = 500, y = 700. So Rs. 500 at 12%, Rs. 700 at 10%. Option D has this.