model 2 at ci sum becomes ‘n’ times after ‘t’ years 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 Tier-I 2010]
A sum of money at compound interest doubles itself in 15 years. It will become eight times of itself in
a) 60 years
b) 45 years
c) 54 years
d) 48 years
Answer »Answer: (b)
A = P$(1 + R/100)^T$
2 = 1$(1 + R/100)^15$
Cubing on both sides, we have
8 = 1$(1 + R/100)^45$
Required time = 45 years
Using Rule 5,
Here, m = 2, t = 15 years
It becomes 8 times = $2^3$ times
in t × n years= 15 × 3 = 45 years
Question : 12 [SSC MTS 2013]
A sum of money becomes 1.331 times in 3 years as compound interest. The rate of interest is
a) 50%
b) 8%
c) 10%
d) 7.5%
Answer »Answer: (c)
If principal = Rs.1000, amount = Rs.1331
A = P$(1 + R/100)^T$
$1331/1000 = (1 + R/100)^3$
$(11/10)^3 = (1 + R/100)^3$
$1 + R/100 = 11/10$
$R/100 = 1/10$
R = $1/10 × 100$ = 10%
Using Rule 8,If a sum becomes 'n' times of itself in 't' years on compound interest, then R% = $[n^{1/t} - 1] × 100%$
Here, n = 1.331, t = 3 years
R% = $(n^{1/t} - 1) × 100%$
= $[(1.331)^{1/3} - 1] × 100%$
= [1.1 - 1] × 100%
= 0.1 × 100% ⇒ R% = 10%
Question : 13 [SSC CGL Tier-II 2012]
A sum of money at compound interest amounts to thrice itself in 3 years. In how many years will it be 9 times itself ?
a) 3 years
b) 9 years
c) 6 years
d) 27 years
Answer »Answer: (c)
A = P$(1 + R/100)^T$
Let P = Rs.1, then A = Rs.3
3 = 1$(1 + R/100)^3$
On squaring both sides,
9 = 1$(1 + R/100)^6$
Time = 6 years
Using Rule 11,
Here, $x = 3, n_1 = 3, y = 9, n_2$ = ?
Using, $x^{1/n_1} = y^{1/n_2}$
$(3)^{1/3} = (9)^{1/n_2}$
$3^{1/3} = (3^2)^{1/n_2}$
$3^{1/3} = 3^{2/n_2}$
$1/3 = 2/n_2 ⇒ n_2$ = 6 years
Question : 14 [SSC CHSL 2013]
If the amount is 3$3/8$ times the sum after 3 years at compound interest compounded annually, then the rate of interest per annum is
a) 33$1/3$%
b) 25%
c) 16$2/3$%
d) 50%
Answer »Answer: (d)
A = P$(1 + R/100)^T$
$27/8x = x(1 + R/100)^3$
$(3/2)^3 = (1 + R/100)^3$
$1 + R/100 = 3/2$
$R/100 = 3/2 - 1 = 1/2$
R = $1/2$ × 100 ⇒ R = 50%
Using Rule 8,
n= $27/8$, t = 3 years
R% = $(n^{1/t} - 1) × 100%$
= $((27/8)^{1/3} - 1) × 100%$
= $[(3/2) - 1]$ × 100% ⇒ R% = 50%
Question : 15 [SSC Investigator 2010]
At what rate percent per annum of compound interest, will a sum of money become four times of itself in two years ?
a) 20%
b) 100%
c) 50%
d) 75%
Answer »Answer: (b)
A = P$(1 + R/100)^T$
4 = $(1 + R/100)^2$
1 + $R/100$ = 2
$R/100$ = 1 ⇒ R = 100%
Using Rule 8,
Here, n = 4, t = 2 years
R% = $(n^{1/t} - 1)$ × 100%
= $((4)^{1/2} - 1)$ × 100% = 100%
IMPORTANT quantitative aptitude EXERCISES
-
500+ Basic Compound Interest MCQs Aptitude Practice Test »
-
Top 499+ Compound Interest MCQs For BANK SSC UPSC Railway »
-
New 455+ Compound Interest Problems Solution for BANK SSC »
-
Top 399+ Compound Interest Questions for UPSC TNPSC Exams »
-
Top 599+ Compound Interest Practice MCQs For SBI IBPS RBI »
-
Top 489+ Compound Interest Practice Sums For All SSC Exam »
model 2 at ci sum becomes ‘n’ times after ‘t’ years Shortcuts »
Click to Read...model 2 at ci sum becomes ‘n’ times after ‘t’ years 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 …
quantitative aptitude CATEGORIES
RECENT BLOGS
Recently Added Subject & Categories For All Competitive Exams
New 100+ Compound Interest MCQ with Answers PDF for IBPS
Compound Interest verbal ability questions and answers solutions with PDF for IBPS RRB PO. Aptitude Objective MCQ Practice Exercises all competitive exams
Continue Reading »
100+ Mixture and Alligation MCQ Questions PDF for IBPS
Most importantly Mixture and Alligation multiple choice questions and answers with PDF for IBPS RRB PO. Aptitude MCQ Practice Exercises all Bank Exams
Continue Reading »
IBPS Profit and Loss Questions Solved Problems with PDF
Most important Profit and Loss multiple choice questions and answers with PDF for IBPS RRB PO. 100+ Aptitude MCQ Practice Exercises all competitive exams
Continue Reading »
100+ Average Aptitude Questions Answers solutions MCQ PDF
New Average multiple choice questions and answers with PDF for IBPS RRB PO. 100+ Quantitative Aptitude MCQ Practice Exercises all competitive exams
Continue Reading »