Question

How many ways can 840 be written as the product of two numbers?

Answer 1

840=1×840
=2×420
=3×280
=4×210
=5×168
=6×140
=7×120
=8×105
=10×84
=12×70
=14×60
=15×56
=20×42
=21×40
=24×35
=28×30

840 can be written as product of two numbers in 16 ways

Answer 2

Factors of 840 is,

$840=7\times 3\times 5\times 2^3$

2, 3, 5, and 7 are the prime number. 3, 1, 1, and 1 are their respective power.

The number of factors is represented by :

$(3+1)(1+1)(1+1)(1+1)=4\times 2\times 2\times 2\\=32$

The number of Ordered pairs of any two factors is,

$\frac{32}{2} = 16$

In 16 ways 840 be written as the product of two numbers.