# Multiplying Bases

• Jan 29th 2010, 08:54 AM
Avitus
Multiplying Bases
I don't understand how to multiply bases.

Ex. 342 base 7
X 3 base 7

I understand that you can only use numbers 0,1,2,3,4,5,6 but I just have no idea what else to do. I don't get how to convert it to base 10.
• Jan 29th 2010, 09:21 AM
TheEmptySet
Quote:

Originally Posted by Avitus
I don't understand how to multiply bases.

Ex. 342 base 7
X 3 base 7

I understand that you can only use numbers 0,1,2,3,4,5,6 but I just have no idea what else to do. I don't get how to convert it to base 10.

It is exactly like multiplying in base ten, just remember where your arithmetic lives (Rock)

$3_7 \cdot 2_7=6_7$

Now the next one is just a bit harder

$3_7 \cdot 4_7=15_7$ why is this true?

Remember that multiplication is just repeated addition i.e

$4_7+4_7=11_7$ i.e we have 1 seven and one left over

$11_7+4_7=15_7$

And for the last one we have

$3_7\cdot 3_7=12_7$

Now when you multiply just use these compuations and don't forget to carry to the next column.

Also remember what base seven really means is

$342_7=3\cdot 7^2+4\cdot 7^1+2\cdot 7^0$

This is just like base 10 i.e

$342=3\cdot 10^2+4\cdot 10^1+2\cdot 10^0$

I hope this helps.