If my age was thrice my sister’s 3 years ago and will be twice her age next year. What is my age?

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william1941's profile pic

william1941 | College Teacher | (Level 3) Valedictorian

Posted on

Let's start with assuming that your sister's age now is S.

Her age 3 years back was equal to S-3

Your age 3 years ago is given as being thrice that your sister's. So your age was 3*(S - 3)

Next year your sister's age will be S+1

And your age next year will be twice year age.

So 3*(S - 3)+4 = 2*(S+1)

=> 3S - 9 +4 = 2S +2

=> S = 2 +9 -4

=> S = 7

So your sister's age is 7.

Your age three years back was 3*(S - 3) = 3* 4 = 12

Therefore you are 15 years old.

neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

My present age of my sister= x assumed.

3 years before her age = x-3.

My  age 3 ters ago =  3tines my sister's age= 3(x-3).

Next year my sister'age = x+1.

My age next year = 3(x-3) + 4 this twice sister's age next year = 2(x+1).

So the required equation is:

3(x-3)+4 = 2(x+1). We solve this.

3x-9 +4= 2x+2

3x-2x = 2+9-4

x = 7.

So my sister' age = 7.

My age = my age next year -1 = 3(x-3)+4 -1 = 3x-9+3 = 3x-6 = 7*3-6 = 15

My age = 15 and my sister's age = 7.

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