Question

the hcf and lcm of two numbers is 10 and 840 if the one number is 120 then what will be the secoend number

Answer 1

Let the second no be x.
Then
LCM ×HCF =product of the two numbers
10×840=120x
x=8400/120
x=70

Answer 2

HCF =10
LCM=840
1st no. =120
Let the second no. be y
we know that :
HCF×LCM=product of two numbers
10×840=120×y
y=(10×840)/120
y=70