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### Lisa HW says

One non-calculator trick (in keeping with this quick-tricks Hub) to do 75% of 40 is to know that 10% of any number can be seen by moving the decimal point over 1 place toward your left hand. With 40, the decimal point isn't seen; but if it were it would be seen this way: 40.0 If you move the decimal point over one place toward your left hand, you'd get 4 (or 4.0). That means that 4 is 10% of 40.

Now that you know 4 is 10% of 40, all you need to do see what 5% is, is to keep in mind that because 5 (%) is half of 10 (%), and since 2 if half of 4 - 5% of 40 is 2.

Since there are 7 10-percents in 70, you'd know that you need to multiply that 4 (which is 10%) by 7. (4 x 7 is 28). That's only 70 percent of 40, so to get 75 percent of 40 you'd need to add that 2 (the 5% you thought of earlier) to the 28. So, 28 (which is 70%) and 2 (which is "that extra 5%) is 30 - and that's the 75%.

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A simpler way (if you know your percents a little) might be to keep in mind that 75 percents is 3 25-percents, and 25 percent is always one-quarter (one-fourth). Since it's easy to see that one-fourth of 40 is 10, all you need to think of is that 3 times that one-fourth (3 times 25%) is 30.

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Another simple approach might be to keep in mind that 75% is 25% fewer than 100%, so if you think up what 25% (one fourth) is, and subtract that from the 40 (which is 100% of 40) - you have your answer. In other words, since you know that 25% (one-quarter) of 40 is 10; all you have to do is subtract 10 (the 25%) from 40 to see what 75% of it is.