Simple and Compound Interest Tricks – 2
Read this post carefully and note down all the formulas in a piece of paper for quick revision.
Q. 1) If a sum of money becomes 3 times itself in 20 years at simple interest. What is the rate of interest?
In such questions apply the direct formula-
Rate of interest = [100*(Multiple factor – 1)]/T
So R = 100*(3 – 1)/20
Answer : 10%
Note : With this formula you can find Rate if Time is given and Time if rate is given.
Q. 2)
We Recommend Testbook APP | |
100+ Free Mocks For RRB NTPC & Group D Exam | Attempt Free Mock Test |
100+ Free Mocks for IBPS & SBI Clerk Exam | Attempt Free Mock Test |
100+ Free Mocks for SSC CGL 2021 Exam | Attempt Free Mock Test |
100+ Free Mocks for Defence Police SI 2021 Exam | Attempt Free Mock Test |
100+ Free Mocks for UPSSSC 2021 Exam | Attempt Free Mock Test |
In such questions, just write this line :
1st part : 2nd part : 3rd part = 1/(100+T1 * r) : 1/(100+T2 * r) : 1/(100+T3 * r)
= 1/(100+2 * 5) : 1/(100+3 * 5) : 1/(100+4*5)
= 1/110 : 1/115 : 1/120
= 23*24 : 22*24 : 23*22
Hence 1st part = (23*24)/ (23*24 + 22*24 + 23*22) * 2379
Answer : 828
Note : Surprisingly, such questions when asked mostly have this same data, i.e., R=5% and T1, T2, T3 = 2, 3, 4 years, respectively. Only the Principal is changed. So it would be wise if you can just mug this line :
1st part : 2nd part : 3rd part = 23*24 : 22*24 : 23*22
Based on the above line, you would be able to solve such questions in a jiffy.
But note that it will only work if the question is on Simple Interest. Like the below question appeared in SSC CGL Tier 2-
Here the data is same. i.e., R=5% and T1, T2, T3 = 2, 3, 4 years, respectively. So we will write directly –
1st part : 2nd part : 3rd part = 23*24 : 22*24 : 23*22
A received = (23*24)/ (23*24 + 22*24 + 23*22) * 7930
Answer : Rs. 2760
Q. 5) If a certain sum of money P lent out for a certain time T amounts to P_{1} at R_{1}% per annum and to P_{2} at R_{2}% per annum, then
Apply the formula:
R = (650-600)*100/600*6 – 650*4
R = 5%
Alternative Method :
Difference between CI and SI
If t=3 years then difference between CI and SI can be given by two formulas-
1.44P = P(1 + r/100)^2
P(1.05^3 – 1) – 0.15P = 244
P = Rs. 32000
A = P(1+r/100)^t
2.5 = 10R – 10r
R – r = 0.25
Answer : (D)
Total CI = 0.05P + 0.0525P = 0.1025P
= [(1587/1200)^1/2 – 1]*100
= 15%
Governmentadda Suggests | ixambee Courses |
RBI Grade B + NABARD Grade A Course | Click Here |
FCI AGM Technical Course | Click Here |
FCI AGM GA Course | Click Here |