Let g be the number of grandchildren, and d be the number of dogs. They both have only one head, so the number of heads is

Grandchildren have 2 legs, while dogs have 4. So, the total number of legs is

From the first equation (the one for the heads) we can derive

Substitute this into the second to get

So, there are 9 dogs and (from the first equation

Hey there! I'm happy to help!
This number is sixty six thousand six hundred eighty one. This means that our ten thousandths place is the first 6.
We look to the right place to see if it is 5 or bigger. It is also six.
Therefore we bump the ten thousands place up 1 to 7 and we make everything else 0, giving us 70,000.
Have a wonderful day! :D
A good way to remember Pi would be 3.1459. You can remember it in a song or just simply repeat it until you can memorize it.