Question

what is a fast way to multiply decimals, eg: 25 x 0.5, 17 x 0.75. also
what is a fast way to multiply 2 digit numbers eg: 90 x 91, 32 x 31.
thx, and ofcourse without using calculators i mean

Answer 1

Well, I write down

90
x91
and then multiply 1x0 then 1x9. After that I multiple 9x0 and then 9x9. Add the two answers!! :DD There you go 8190

Answer 2

:o!

Answer 3

tyvm!

Answer 4

For the decimal one. Think your adding coins. .25.+.50! It's .75! :3

Answer 5

hmm ok

Answer 6

If you have simple decimals with only 2 decimal places e.g. 0.75 you can just mulitply by 75 and then divide by 100 at the end by just shifting the decimal point 2 places to the left.

Answer 7

If it's something hard like,

.0192*.473

It's pretty simple. the same as multiplying!

.0192
x.274
_______
8
36
4
0
14
63
7
0
4
18
2
0
______ add all of that up!
.0052608

how do you know where to put the decimals? add each number to right of the decimal!

.0192=4
.274=3
_________
8 numbers to the left.

If you don't have eight numbers you add zeros until you right 8! :DD Yay!

Answer 8

until you have 8**