Just subtract what is obvious first and then the rest. It is usually better to subtract numbers in two steps instead of one, rounding the first to the closest hundredth and subtracting the added number to the second. When subtracting 5 from a number whose last digit is less than 5, first subtract 10 and then add 5. For example: 23-5 =
The two 5s cancel out with the 10, -3-6 and +9 cancel out as well and we are left with 14+4-8-3+14-2=19ĩ60+19=979 SUBTRACTION RULE #1: subtracting 5 Even though it sounds tedious and confusing, the following example shows that the method is very efficient. Finally, simply multiply the average by the number of addends and add the result of the previous sum. When adding a long list of numbers, estimate the average of the list ( the closer the average, the easier it gets), then just add the difference of each number and the average. When adding 5 to a number whose last digit is greater than 5, first subtract 5 and then add 10. For example: 18 + 5 = 23 When dealing with large numbers it is often easier to add a single digit at a time instead of trying to add the whole number. This trick may not work for everyone but it is useful to know. In general, you can add what comes easy to you first and then add the rest, as in the following example: 2074 + 254 = 2100 + (254 - 26) = 2100 + 228 = 2328. It is usually better to add numbers in two steps instead of one, rounding the first to the closest hundredth and subtracting the added number to the second.
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