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A sum of money triples in 5 years at simple interest. What will be the rate of interest per annum?
Let the principal be P . It's said in the question that the money triples itself in 5 years. So, the amount after 5 years is 3P. So, the simple intrest = Amount - Principal = 3P - P = 2P. Now we know both the principal and simple intrest so we can use the formula of SI to find the answer. ( P * R *Read more
Let the principal be P .
It’s said in the question that the money triples itself in 5 years. So, the amount after 5 years is 3P.
So, the simple intrest = Amount – Principal = 3P – P = 2P.
Now we know both the principal and simple intrest so we can use the formula of SI to find the answer.
( P * R * T ) / 100 = SI
= (P * R * 5 ) / 100 = 2P
= R / 20 = 2P / P
= R = 2 * 20 = 40%
Alternatively , there is a simple shortcut to this.
When the question says the principal becomes n times in T years.
Then , R * T = ( n – 1 ) 100
In this case, R * T = (3 -1 ) 100
= R * 5 = 200
= R = 200 / 5 = 40%
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