To multiply together 2-digit numbers ending in 5: ex. 25×45=1125
-If the difference in tens digits of the numbers being multiplied is even, the last 2 digits of the answer is 25. ex. the difference between 2 and 4 is 2, which is even, giving _ _25
-Multiply (lower tens digit) times (1+higher tens digit). To this add half the difference between them. This yields the first digits of the answer. ex. 2 times (4+1) + (half of 2) = 11_ _
-If the difference in tens digits of the numbers being multiplied is odd, the last 2 digits of the answer is 75, as in 15×45=675
-Continue the second step above multiplying (lower tens digit) times (1+higher tens digit). Add half the difference between them, as above, throwing away the fraction for the first digits of the answer. 1 times (4+1) + half of 3 = 6_ _ The fraction is thrown away.
Try: 15×55=825 15×65=975 75×86=6375 35×65=2275 45×95=4275
