Aptitude Shortcuts and Mind Tricks to Find Simple Interest and Compound Interest (1)

8/15/2019 Aptitude Shortcuts and Mind Tricks to Find Simple Interest and Compound Interest (1)

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Aptitude Shortcuts and Mind Tricks to Find Simple Interest and Compound Interest:

Question:

1). What is the compound interest occurred on a principle of amount of Rs. 12,000 at the rate

of interest 4% per annum after the period of 2 years?

Given:-

Principle amount (P) – Rs. 12,000

Rate of interest (R) - 4%

Time Period (T) - 2 years.

Normal Method:

Compound Amount- P × (1 +

100) T

Compound Interest- Compound Amount – Principle Amount

Substitute the given data in the above formula, then I will become as,

C.A= 12,000 × (1 + 4100

) 2

= 12,000 × ( 104100

) 2

= 12,000 × (1.04) 2

= 12,000 × 1.0816

= 12,979.2

Then,

Compound Interest- Compound Amount – Principle Amount


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C.I= 12,979.2 – 12,000

C.I= 979.2

Answers is: 979 2

If you use this method it will take more than 1 minute to solve this problem. Here we have an

easily shortcut to solve this problem with in 20 second.

Shortcut Method:

Step 1:

Find 4% in 12,000

Answer is: 480

(Consider 12,000 as 100%, then 1% = 120, and 4% = 120 × 4, your answer is 480)

This is for First year, 2 years, 480 × 2 = 960.

Step-2:

Divide the given rate of interest by 2.

= 4%2

= 2%.

Now, find 2% in 960 (take the answer from step 1)

= 19.2

Add Step 1 and Step 2:

= 960 + 19.2


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= 979.2

Answer is: 979 2

Note: This shortcut method is applicable to find the compound interest, only when the given

time period is 2 years.

Examples Questions :

1). What is the compound interest occurred on a principle of amount of Rs. 8,000 at the rate of

interest 3% per annum after the period of 2 years?

Shortcut method:

Step 1:

Find 3% in 8,000

Answer is: 240

This is for First year, in sum they asking for 2 years so, 240 × 2 = 480.

Step-2:


= 3%2

= 1.5%.

Now, find 1.5% in 480 (take the answer from step 1)

= 7.2

Add Step 1 and Step 2:

= 480 + 7.2

= 487.2Answer is: 487 2

2). What is the compound interest occurred on a principle of amount of Rs. 15,000 at the rate

of interest 5% per annum after the period of 2 years?

Step 1:


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Find 5% in 15,000

Answer is: 750

For Two Years, 750 × 2 = 1500.

Step-2:


= 5%2

= 2.5%.

Now, find 2.5% in 1500 (take the answer from step 1)

= 37.2

Add Step 1 and Step 2:= 1500 + 37.2 , = 1537.2

Answer is: 1537 2

If you have any doubt in the above shortcut methods feel free to contact us,

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Aptitude Shortcuts and Mind Tricks to Find Simple Interest and Compound Interest (1)