Example 1: If Rs. 4000 is invested at 8% p.a. simple interest for 5 years, find the interest. Show
Sol: simple interest formula: 4000 × 8 × 5/100 = Rs. 1600 Example 2: If Rs 16,000 is invested at 12 percent simple annual interest, how much interest is earned after 6 months? Sol: Since the annual interest rate is 12 %, the interest for 6 months is (16000x12x6)/12x100 = Rs. 960.
Example 3: A sum was put at simple interest at a certain rate for 6 years. Had it been put at 2 % higher rate, it would have earned Rs 120 more. Find the sum. Sol: Let P be the principal and x be the original % rate of interest. The interest for 6 years will
amount to 6Px/100. If the rate is increased by 2%, the new interest then becomes 6P(x + 2)/100. The difference between the two is c 6P(x + 2)/100 - 6Px/100 = 6P × 2/100. Example 4:An amount of Rs. 8000 is lent out in two parts such that the interest on first part at 15 % for 4 years is equal to interest on second part at 4 % for 10 years. Find the sum lent out at 15%. Sol: Let P be the sum
lent out at 15% and Q be the sum lent out at 4%. So Px.15x4 = Qx.04×10 Example 5: Shamrao deposits Rs 2,000 in his savings account at Bank of Maharashtra at 4% and Rs 3,000 in US – 64 at 14% p.a. Find the rate of interest for the whole sum. Sol: Shamrao earns an interest of Rs 0.04 x 2000 = Rs. 80 in the
Bank of Maharashtra account. Example 6: A Sum of money at simple interest of 20% p.a. will take how many years to double itself? Sol: Let the Principal be Rs. 100. The amount after the specified time = Rs. 200.
Example 7: What sum of money amounts to Rs. 3900 in 2 years at 15% p.a. Simple Interest? Sol: Using the formula and putting the values, we get
Example 8: A sum of money amounts to Rs. 9600 in 2 years at 10% p.a. Find the simple interest. Sol:
Using the formula, and putting the values, we get Example 9: A certain sum of money amounts to Rs. 630 in 2 years and to Rs. 675 in 5 years. Find the sum and the rate of interest. Sol: P + (S.I. for 5 years) = Rs. 675 and P + (S.I. for 2 years) = Rs. 630. Example 10: What annual installment will discharge a loan of Rs. 5900, due after 5 years, the rate of interest being 9 % per annum? Sol:
The first error, the student can make in this case, is if she treats Rs. 5900 as the principal. The following method should be applied to solve this kind of question.
What is the time in years in which a sum of Rs 4000 will yield a simple interest of Rs 1200 at 12 per annum?Thus, the time in which a sum of Rs. 4000 will yield a simple interest in Rs. 1200 at 12% per year is 2.5 years.
At what rate% per annum will a sum of ₹ 4000 yield compound interest of ₹ 410 in 2 years?∴ Rate =5% p.a.
At what rate percent will a sum of ₹ 4000 yield ₹ 1324 as compound interest in three years?Thus, the rate of interest is 10%.
How many years will a sum of Rs 3000 in a simple interest of Rs 1080 at 12% per annum?6. A sum of ₹ 3,000/- yields an interest of ₹ 1,080/- at 12% per annum simple interest in how many years? 4 years.
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