how to divide the following mentally without a calculator: (4×10^−4)÷(8×10^−6)?

(4 × 10^−4) ÷ (8 × 10^−6)
= (4 / 10^4) / (8 / 10^6)
= (4 × 10^6) / (8 × 10^4)
= (4 × 10^3) / (8 × 10^1)
= 4000 / 80
= 50

(4.10^(-4))/8(10^(-6))
=4 ( 10^(-4)) 10^6 / 8
= 100 / 2 = 50

= [4 * 10^(- 4)] / [8 * 10^(- 6)]

= [4 * 10^(- 4)] / [2 * 4 * 10^(- 6)]

= 10^(- 4) / [2 * 10^(- 6)]

= 10^(- 4) * 10^(6) / 2

= 10^(- 4 + 6) / 2

= 10^(2) / 2

= 100/2

= 50

4/8=0.5
10^-4/10^-6= 10^2
(4×10^−4)÷(8×10^−6)= 0.5*10^2= 50

0.0004 / 0.000008 or 400 / 8 or 50
mentally, change exponents to be same
400 x 10^-6 divided by 8 X 10^-6.

you have 4 ( 10^(-4)) 10^6 / 8 = 100 / 2 = 50

rewrite as:

= 4/10000 divided by 8/1000000
(cross multiply)
= 4000000 / 80000
= 2000000 / 40000
= 1000000 / 20000
.
.
.
= 50