Not allowed to use calculator

[liamboyle06]

Hi All, what a great Friday Morning

I am not allowed to use a calculator(could however) but for a Paper I am doing, I need to Multiple 39.6 by 49.5 and show all the long calculations for it.
I already did the approx one and got 2000, but how do I multiple the decimals and add them in and record it all down?

Any suggestions would be very beneficial.

[danielf]

Originally Posted by liamboyle06

Hi All, what a great Friday Morning

I am not allowed to use a calculator(could however) but for a Paper I am doing, I need to Multiple 39.6 by 49.5 and show all the long calculations for it.
I already did the approx one and got 2000, but how do I multiple the decimals and add them in and record it all down?

Any suggestions would be very beneficial.

Multiply 39.6 by 50. 50*39.6 = 5* 396 = 5*400 - (5*4) = 2000 - 20 = 1980
Now subtract 0.5 * 39.6 = 19.8

1980 - 19.8 = 1960.2 Easy...

[bmxbandit]

http://www.google.co.uk/search?q=long+multiplication

a plethora of info

[NitroNutter]

39.6
*49.5
-------
39.6 * 5 answer here
39.6 * 9 answer here with a 0 at the end
39.6 * 4 answer here with 00 at the end
--------
add the 3 answers and the decimal point does not move, it follows the same line all the way down

[basa]

Originally Posted by danielf

Multiply 39.6 by 50. 50*39.6 = 5* 396 = 5*400 - (5*4) = 2000 - 20 = 1980
Now subtract 0.5 * 39.6 = 19.8

1980 - 19.8 = 1960.2 Easy...

Or 39.6 x 100 (move dec point two places right) = 3960, divide by 2 = 1980

similarly 39.6 x 1 = 39.6 / 2 = 19.8

1980 - 19.8 = 1960.2

[altis]

I can do it all in one line:

http://www.google.co.uk/search?q=39.6+*49.5

[liamboyle06]

Thanks all for your advice
I used the BBC's site which was a great help.
http://www.bbc.co.uk/schools/gcsebit...hs/42046.shtml