model 3 combination of si & ci Practice Questions Answers Test with Solutions & More Shortcuts
compound interest PRACTICE TEST [6 - EXERCISES]
model 1 basic compound interest using formula
model 2 at ci sum becomes ‘n’ times after ‘t’ years
model 3 combination of si & ci
model 4 difference in ci & si
model 5 ci with instalments
model 6 comparing sum in different years
Question : 11 [SSC CGL Prelim 2008]
At a certain rate per annum, the simple interest on a sum of money for one year is Rs.260 and the compound interest on the same sum for two years is Rs.540.80. The rate of interest per annum is
a) 10%
b) 4%
c) 8%
d) 6%
Answer »Answer: (c)
Using Rule 1,If A = Amount, P = Principal, r = Rate of Compound Interest (C.I.), n = no. of years then,A=P$(1 + r/100)^n$, C.I. = A - PC.I. = P$[(1 + r/100)^n - 1]$
Let the principal be x and rate of interest be r% per annum. Now,
S.I. = $\text"Principal × Time × Rate"/100$
260 = ${x × r}/100$ ....(i)
C.I.= P$[(1 + R/100)^T - 1]$
540.80 = $x[(1 + r/100)^2 - 1]$
540.80 = $x[1 + {2r}/100 + r^2/10000 - 1]$
540.80 = ${2xr}/100 + {xr^2}/10000$
540.80 = 2 × 260 + ${260 . r}/100$
260r = 54080 - 52000
260r = 2080
r = $2080/260$ = 8 %
Question : 12 [SSC MTS 2013]
If the compound interest on a certain sum for 2 years at 4% p.a. is Rs.102, the simple interest at the same rate of interest for two years would be
a) Rs.100
b) Rs.200
c) Rs.150
d) Rs.50
Answer »Answer: (a)
If the sum be P, then
C.I. = P$[(1 + R/100)^T - 1]$
102 = $[(1 + 4/100)^2 - 1]$
102 = P$[(26/25)^2 - 1]$
102 = P$(676/625 - 1)$
102 = P$({676 - 625}/625)$
102 = P × $51/625$
P = ${102 × 625}/51$ = Rs.1250
S.I. = ${1250 × 2 × 4}/100$ = Rs.100
Question : 13 [SSC Sub-Inspector 2013]
A sum becomes Rs.2,916 in 2 years at 8% per annum compound interest. The simple interest at 9% per annum for 3 years on the same amount will be
a) Rs.625
b) Rs.600
c) Rs.650
d) Rs.675
Answer »Answer: (d)
Using Rule 1,
A = P$(1 + R/100)^T$
2916 = $x(1 + 8/100)^2$
2916 = $x(27/25)^2$
$x = {2916 × 25 × 25}/{27 × 27}$ = Rs.2500
S.I. = ${P × R × T}/100$
= ${2500 × 9 × 3}/100$ = Rs.675
Question : 14 [SSC CGL Prelim 2004]
If the compound interest on a sum for 2 years at 12$1/2$% per annum is Rs.510, the simple interest on the same sum at the same rate for the same period of time is :
a) Rs.460
b) Rs.400
c) Rs.450
d) Rs.480
Answer »Answer: (d)
C.I. = P$[(1 + R/100)^T - 1]$
510 = P$[(1 + 25/200)^2 - 1]$
510 = P$(81/64 - 1)$
P = ${510 × 64}/17$ = 1920
S.I. = ${1920 × 2 × 25}/{100 × 2}$ = Rs.480
Using Rule 10,
Here, C.I. = Rs.510, R = 12$1/2$%, S.I. = ?
C.I. = S.I.$(1 + R/200)$
$510 = S.I.(1 + 25/400)$
S.I. = ${510 × 400}/425$ = Rs.480
Question : 15 [SSC CGL Tier-II 2014]
If the compound interest on a sum for 2 years at 12$1/2$ p.a is Rs.510, the simple interest on the same sum at the same rate for the same period of time is
a) Rs.480
b) Rs.400
c) Rs.460
d) Rs.450
Answer »Answer: (a)
Principal = Rs.P (let)
C.I. = P$[(1 + R/100)^T - 1]$
510 = P$[(1 + 25/200)^2 - 1]$
510 = P$[(1 + 1/8)^2 - 1]$
510 = P$[(9/8)^2 - 1]$
510 = P$(81/64 - 1)$
510 = P$({81 - 64}/64)$
510 = ${17P}/64$
P = ${510 × 64}/17$ = Rs.1920
S.I. = $\text"Principal × Time × Rate"/100$
= ${1920 × 2 × 25}/{100 × 2}$ = Rs.480
Using Rule 10,
Here, C.I. = Rs.510, R = 12$1/2$%, S.I. = ?
C.I. = S.I.$(1 + R/200)$
510 = S.I.$(1 + 25/400)$
510 = S.I.$(425/400)$
S.I. = ${510 × 400}/425$ = Rs.480
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model 3 combination of si & ci Shortcuts »
Click to Read...model 3 combination of si & ci Online Quiz
Click to Start..compound interest Shortcuts and Techniques with Examples
-
model 1 basic compound interest using formula
Defination & Shortcuts … -
model 2 at ci sum becomes ‘n’ times after ‘t’ years
Defination & Shortcuts … -
model 3 combination of si & ci
Defination & Shortcuts … -
model 4 difference in ci & si
Defination & Shortcuts … -
model 5 ci with instalments
Defination & Shortcuts … -
model 6 comparing sum in different years
Defination & Shortcuts …
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