PROBLEMS ON CALCULATION OF TIME Time of the Cl can be calculated either by the long formula or Just by using the common sense. Time also depends how the rate is charged. Lets move on to the questions and we will see how easy is to calculate the time
Q1. In what time the Rs.2000 will become Rs.2880 compounded annually at the rate of 20% pa Now 20% pa = So 5 units is the principal and 6 units is the amount for 1 year. Comparing both values of principal and amount and writing in simplest form 5 2880 by 8 we get 36 = (6/5)2 = (6/5)' 2000 25 Now by comparing we get t= 2 years
Q2. In how many years Rs.1000 will become Rs.1331 at 20% per annum compounded half yearly? As the Cl is compounded half yearly so new rate-10% pa = 10 Taking the ratio of the given amount-1331 =(11/103 (11/10)' 1000 By comparing the bases we get t= 3years 3 But the CI is compounded half yearly so original time = (-)-1.5 years 2
Q3. If a certain sum, at compound interest become double in 5 yr, then in how many years, it will become 16 time at same rate of interest? Now it become 2 times in 5 yr. 16 times = 24 of itself in 5x4 = 20 yr.
Q4. At compound interest, if a certain sum of money doubles itself in t yr, then the amount will be eight fold in: So the money becomes 2 times in t yr It will become 8 times= 23-3 t = 3t yrs.
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