SAT Math tip: Find Percentages easily
Find out percentages of a number within a few seconds.
Typically you will get some question in the SAT exam about finding percentages of a number. I will teach you how it is easy to estimate percentages within a few seconds.
Prerequisite: You should know simple basic facts about multiplying combination of numbers between 1 to 10. In short, you should know multiplication tables for at least numbers 1 to 10. If you know more than that, it will be great.
So lets try the simple numbers.
(a) 10% of any number.
Rule: Take the number and go 1 place to the left of the digit immediately after the decimal pointand add a decimal point there. EASY!!
e.g. 10% of 210 is 21.0. Just go 1 place to the left of the last number of the decimal point. In this case the number has no decimal which means the decimal is after the last number which is 0. 1 place to left of zero is 1 and place a decimal point after 1, so the answer is 21.0.
10% of 23.82 is 2.382. Just go 1 place to the left of the digit immediately after the decimal which is 8. 1 place to left of 8 is 3 and place a decimal point after 3, so the answer is 2.382.
(b) 5% of any number
If you are comfortable doing 10% of a number, do it and divide by 2.
So, 5% of 210:
10% of 210 is 21.0 and half of 21.0 is 10.5
Hence, 5% of 210 is 10.5
So, 5% of 23.82
10% of 23.82 is 2.382 and half of 2.382 is 1.191
so, 5% of 23.82 is 1.191.