Question: If the simple interest on a sum of money at 5% per annum for 3 years is Tk. 1200, the compound interest on the same sum for the same period at the same rate, is:
A
Tk. 1260
B
Tk. 1261
C
Tk. 1264
D
Tk. 1265
Note: Sum=Tk. `((100 xx 1200)/(3 xx 5))` = Tk. 8000
Amount = Tk. `[8000 xx (1 + 5/100)^3]`
Tk. = `(8000 xx 21/20 xx 21/20 xx 21/20)`
`:.` C.I. = Tk. (9261 - 8000) = Tk. 1261
Question: The difference between the compound interest and the simple interest on a sum of money for two years at `12 1/2 %` per annum is Tk. 150 The sum is:
A
Tk. 9000
B
Tk. 9200
C
Tk 9500
D
Tk 9600
Note: Let the sum be Tk. `x.` Then,
C.I.
`= x ( 1 + 25/(2 xx 100))^2 - x `
`= (9/8 xx 9/8)x - x`
`= (17x)/64`
S.I. =`( x xx 25/2 xx 1/100)`
` = x/4`
(C.I) - (S.I)
`= ((17x)/64 - x/4)`
`= x/64`
`:. x/64`
`= 150`or
`x=9600`
Question: If the difference between the compound interest, compounded half yearly and the simple interest on a sum at 10% per annum for one year is Tk. 25, the sum is:
A
Tk. 9000
B
Tk 9500
C
Tk 10000
D
10,500
Note: Let the sum be Tk. `x.` Then,
C.I. = `x(1 + 5/100)^2 - x = ((441x)/400 - x) = (41x)/400.`
S.I. = `(x xx 10 xx 1)/100 = x/10`
(C.I) - (S.I) = `(41x)/400 - x/10 = x/400`
`:. x/400 = 25 or x = 10000`
Hence, the sum is Tk. 10000.