Question

4. The sum of two numbers is 10 and their product is 21. What are the two numbers?

Answer 1

$\Large{\sf{\blue{Sol}\pink{ution} }}$

Let the two numbers be x and y

Their sum is 10 so numbers must be less than 10

Therefore both x and y are single digit numbers in the range [1....9]

pairs of numbers adding to 10

» 1+9 product is 9

» 2+8 product is 16

» 3+7 product is 21

» 4+6 product is 24 (a possibility)

» 5+5 product is 25 (a possibility)

Here we can see only one pair is there whose sum is 10 and product is 21 ie.${\sf\bold{3~and~7}}$

$\large{\sf{.°.~3~and~7~are~the~2~numbers}}$

Answer 2

$if \: x = 3 \: then \: y = \frac{21}{y} = \frac{21}{3 } then \: y = 7 \\ if \: x = 7 \: then \: y = \frac{21}{y} = \frac{21}{7} then \: y = 3$