SBI PO – 2015 – 21

Question:  Two equal amount of money are deposited in two banks each at 5% per annum for 3 and 4 years respectively. If the difference between their simple interests is Rs. 42, find each sum. [5% प्रति वर्ष साधारण व्याज की दर से 3 तथा 4 वर्षों के लिए किसी समान धन के साधारण ब्याज का अंतर 42 रूपये है; तो वह धन क्या है?]  Ans. (d) Rs. 840         

(a) Rs. 210        (b) Rs. 280      (c) Rs. 750      (d) Rs. 840     (e) none of these

 

Detailed Explanation:

First method: Principal is always taken as 100%

Since rate of interest is 5% per annum, so interest for one year (4 - 3) will be 5% × 1 = 5%

5% is equivalent to Rs 42, so 100% will be 20 times of Rs 42, that is Rs 840 Ans.

Second Method: At the rate of 5% per annum, the SI for 3 years is 15% and SI for 4 years is 20%, so the difference is (20 -15)% = 5%. 5% of Principal = Rs 42. So, Principal is (42×100)/5   = Rs 840 Ans.

Third Method: Using (PRT/100), we solve as shown above.