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What is 15*9.

Guest Oct 10, 2017
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#1
+18
+1

\(15*9=135\)

ChowMein  Oct 10, 2017
#2
+1227
+1

135, break it up

tertre  Oct 10, 2017
#3
+1493
+2

This may help, if multiplying by 9 mentally is difficult. A lot of these mental tricks I wish I knew earlier on.

 \(15*9\) Let's make it simpler. \(15(10-1)\) Obviously, this is the same thing. Now, distribute the 15 to both terms. \(15*10-15*1\) Now, simplify. This is much easier, don't you think? \(150-15\) And just in case borrowing is another mental headache... \(150-(20-5)\) Yet again, I have not changed the expression at all. \(150-20+5\) Simplify. \(130+5\) \(135\)

This may look like a lot of steps, but all we are doing is making the problem easier. With practice, this will simplify multiplication with large numbers.

TheXSquaredFactor  Oct 10, 2017

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