Square of two numbers having 5 as last digitMultiplying two similar numbers having 5 as the right most digit is very simple.Example 185 x 85Of '8' and '5', multiply 5 with 5 getting 25 Ans 25Now multiply remaining number (i.e. 8) with
next higher number i.e. 9. So 9 x 8 = 72 Ans 72The answer is 7225Example 265 x 65Step 1
Multiply 5 with 5 i.e. 5 x 5 =25Step 2
Multiply 6 with next higher number i.e. 7 , So it becomes 7 x 6 =42Ans = 4225.Example 335 x 35Step 15 x 5 = 25Step 24 x 3 = 12Ans = 1225Example 4125 x 125Step 1 :
5 x 5 = 25Step 2 :
13x12 = 156Ans = 15625Example 575 x 75Step 1 : 5 x 5 =25
Step 2 : 8 x 7=56
Ans = 5625This formula also holds good when we multiply two number having first digit/s same and total of last digits is 10.Let me make the things clear27x23, 48x42, 89x81, 76x74, 127x123Here in all the five cases the first digit is same and total of 2nd digits in every case is 10.e.g. in 27x23, first digit of both '27' and '23' is same i.e. '2', and total of 2nd digits is 10 (7+3=10)The multiplication in such cases is simplei.e. multiply the last two digits and multiply the first digit with next higher number and the problem is solvedTake for example 27x23Step 1 :
multiply '7 of 27'with '3 of 23' i.e. 7x3=21 AnsStep 2 :
multiply 2 with next higher number i.e. 3 i.e. 3x2=6 AnsSo answer for 27x23 is 621.Similarly48x42
Multiply last digits i.e. 8x2=16multiply first digit (4) with next higher number (5)=20The answer is 2016.In the same way89x81 : 9x1=09 and 8x9=72 Ans is 7209
76x74 : 6x4=24 and 7x8=56 Ans is 5624
127x123 7x3=21 and 12x13=156 Ans is 15621For more such tricks and tactics to make your math simpler, please logon to http://www.magicwithmath.com
Rajinder Goswami
Keyword : math,simple math,mental math,math tutorials,easy math,multiply,multiplication,home work
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