65th Problem 2016

Algebra Level 2

7 years from now, Jack will be 10 years older than Karl. If 15 years ago, Jack was 21 years old, how old is Karl now?

Check out the set: 2016 Problems


The answer is 26.

Angela Fajardo by Angela Fajardo , 19, Philippines

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2 solutions

Angela Fajardo
Mar 19, 2016

1 Helpful 0 Interesting 0 Brilliant 0 Confused

Today\Now\Present

K = K = a g e age o f of K a r l Karl

J = J = a g e age o f of J a c k Jack

7 Years from now

J + 7 = 10 + ( K + 7 ) J + 7 = 10 + (K + 7)

After simplifying the above equation, we get

K = J − 10 K = J - 10 ⟹ \implies e q u a t i o n equation 1 1

15 Years ago

J − 15 = 21 J - 15 = 21

After simplifying the above equation, we get

J = 36 J = 36

From equation 1, solve for the present age of K a r l Karl

K = 36 − 10 = K = 36 - 10 = 26 \boxed{26}

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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