Answer: 5%
Explanation 1:
20:400*100 =
(20*100):400 =
2000:400 = 5
Explanation 2:
Step 1: We make the assumption that 400 is 100% since it is our output value.
Step 2: We next represent the value we seek with $x$x.
Step 3: From step 1, it follows that $100\%=400$100%=400.
Step 4: In the same vein, $x\%=20$x%=20.
Step 5: This gives us a pair of simple equations:
$100\%=400(1)$100%=400(1).
$x\%=20(2)$x%=20(2).
Step 6: By simply dividing equation 1 by equation 2 and taking note of the fact that both the LHS
(left hand side) of both equations have the same unit (%); we have
$\frac{100\%}{x\%}=\frac{400}{20}$
100%
x%=
400
20
Step 7: Taking the inverse (or reciprocal) of both sides yields
$\frac{x\%}{100\%}=\frac{20}{400}$
x%
100%=
20
400
$\Rightarrow x=5\%$⇒x=5%
Therefore, $20$20 is $5\%$5% of $400$400.