Start by rounding 510 and finding 1 % of the rounded number.
About 2
Practice makes perfect
We want to estimate 0.4 % of 510. We will start by rounding 510.
rcl
510 & ≈ & 500
Now we can find 0.4 % of 500 to get an estimation. To do so, let's start by finding 1 % of 500 by multiplying these two quantities. Recall that 1 % is equal to 1100.
We found that 1 % of 500 is equal to 5. Now let's find 0.4 % of 500. We can do this using the fact that 0.4 % is 0.4 of 1 %.
rcr
1 %of 500 & = & 5 [0.3em] & ↓ & [0.3em]
0.4of 1 %of 500 & = & 0.4of5 [0.3em] & ↓ & [0.3em]
0.4 %of 500 & = & 0.4of5
Finally, let's calculate 0.4 of 5 by multiplying these two numbers. This will give is the desired estimation.
