Choose two numbers nearing 100
Let's say 98 and 96
Step 1: Subtract both numbers from 100 and write difference next to them.
9 8 | -2 =>(100-98)
* 9 6 | -4=>(100-96)
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Step 2: Now either subtract 4 from 98 or 2 from 96 it gives 94 only and then multiply 94 with 100 so it gives 9400.
9 8 \ / -2
* 9 6 / \ -4
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(98-4)*100 / (96-2)*100= 9400
Step 3: Now add partial answer 9400 and answer obtained by multiplying the differences with signs.
That is 9400 + (+8), where (-2)*(-4)=+8. (2*4=8 and - , - => +).
9 8 -2
||----(-2*-4)
* 9 6 -4
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9400 + ((-2)*(-4)) = 9400+(+8)= 9408
Thus Final Answer is 9408.
Now similarly take any other digit say one is greater than 100 and other less than hundred (both nearing 100).
let's take 97 and 106
Step 1:
1 0 6 | +6 (100+6=106)
* 9 7 | -3 (100-3=97)
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Step 2:
1 0 6 | +6
* 9 7 | -3
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10300 (106-3*100/97+6*100)
Step 3:
1 0 6 | +6
* 9 7 | -3
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10300+((+6)*(-3))=10300+(-18)
= 10300-18
= 10282
Thus Final Answer is 10282
Thus try to do it orally for increasing your calculation speed.
Practice sums and with the answer
1. 93 and 98=9100+(-2*-7)=9100+14=9114
2. 102 and 95=9700+(+2*-5)=9700-10=9690
3. 101 and 108=10900+(+1*+8)=10900+(+8)=10908
keep on practicing.