Question

explain why 7 x 13 x 11 + 11 and (7 x 6 x 5 x 4 x 3 x 2 multiply 1)+3 are composite nos

Answer 1

Answer:

I hope it is helpful...............

Answer 2

To multiply any number by 11 do the following:

Working from right to left

Write the rightmost digit of the starting number down.

Add each pair of digits and write the results down, (carrying digits where necessary right to left).

Finally write down the left most digit (adding any final carry if necessary).

It's as simple as that, e.g.

Multiply 712x11

 

   

${\displaystyle {\begin{matrix}&7&&1&&2\\&\swarrow \searrow &+&\swarrow \searrow &+&\swarrow \searrow \\7&&8&&3&&2\end{matrix}}}$

 

${\displaystyle {\begin{matrix}&7&&1&&2\\&\swarrow \searrow &+&\swarrow \searrow &+&\swarrow \searrow \\7&&8&&3&&2\end{matrix}}}$

712x11=7832

The reason for working from right to left instead of the more usual left to right is so any carries can be added in. e.g.

Multiply 8738x11

 

   

${\displaystyle {\begin{matrix}&8&&7&&3&&8\\&\swarrow \searrow &+&\swarrow \searrow &+&\swarrow \searrow &+&\swarrow \searrow \\9&\leftarrow _{1}&6&\leftarrow _{1}&1&\leftarrow _{1}&1&&8\end{matrix}}}$

 

${\displaystyle {\begin{matrix}&8&&7&&3&&8\\&\swarrow \searrow &+&\swarrow \searrow &+&\swarrow \searrow &+&\swarrow \searrow \\9&\leftarrow _{1}&6&\leftarrow _{1}&1&\leftarrow _{1}&1&&8\end{matrix}}}$

8738x11=96118

Multiplying by 15

Multiplying by 15 can be broken down into a multiplication by 10 plus a multiplication by 5. Multiplying by 10 is just a matter of adding a 0 on the end of a number, multiplying by 5 is half of a multiplication by 10 as above e.g.