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How do you calculate 180*1.15 in your head without a calculator?

I have search for this thing for 30 minutes and still no answer.

 Oct 25, 2018
 #1
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+1

180 x 1.15 =

Start with a 1 to the left of the decimal in 1.15. Multiply that 1 x 180 =180

Then continue with 1 to the right of the decimal x 180/10                   =18 + 180 =198

Then continue with 5 to the right of the decimal x 180/100   =900/100=9 +198 =207

 Oct 25, 2018
 #2
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+1

Or look at it as 100% of 180 + 10% of 180 + 5% of 180

 

100% of 180 = 180

10% of 180 = 18

5% of 180 = Half of 10% of 180 = 18/2 = 9

 

180+18+9 = 207

 Oct 25, 2018

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