Multiple choice

Mohan borrowed Rs. 720 from Amit at 8% p.a. simple interest for 2 years. He then added some more money to the borrowed sum and lent it to his friend Rahul for the same period of time at 10% p.a. simple interest. If Mohan gains Rs. 77.50 in the whole transaction, then how much money did he add from his side?

  1. Rs. 298

  2. Rs. 243.50

  3. Rs. 198.50

  4. Rs. 156

  5. Rs. 121
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mohan's interest paid is 720 * 0.08 * 2 = 115.2. Let X be the added amount. Total principal is 720 + X. Interest earned is (720 + X) * 0.10 * 2 = 144 + 0.2X. Profit is (144 + 0.2X) - 115.2 = 77.5. Solving 28.8 + 0.2X = 77.5 gives 0.2X = 48.7, so X = 243.5.

AI explanation

Mohan pays simple interest to Amit of Rs. 720 times 8 times 2 divided by 100, which equals Rs. 115.20. Let the added money be x, so the total amount lent to Rahul is 720 + x, and the interest received is (720 + x) times 10 times 2 divided by 100, or 144 + 0.20x. His gain is the difference between the interest received and paid, so 144 + 0.20x minus 115.20 equals 77.50. Solving this gives 0.20x = 48.70, making x equal to Rs. 243.50.

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