Science trouble

Rather than do your math homework for you… try listing the number of grains of rice on each square (1, 2, 4, …), and the total grains of rice so far(3, 7, …), and see if you see a pattern. Let us know how you get on.

this isnt math homework I dont even have to do it , I just want to figure it out

oh and by the way I havnt figured it out… yet lol

hang on.. going to try work it out

nup no idea

see ya later I’ve got thinking to do

Guess I’ll just give it away, then…

If each square has twice as many grains as the previous one, the number of grains on each square goes 1, 2, 4, 8, 16, … - each square has twice as many as the previous one.

Thus, the number of grains of rice on the 5th square is 2 multiplied by itself 4 times. The number of grains on the ‘n’th square is 2 multiplied by itself ‘n-1’ times. This is usually written as 2^(n-1) (or 2 with a superscript n-1, but I can’t represent that here). Numbers of this form are known as ‘powers of 2’.

If you add up the total number of grains of rice on the first 2 squares, 3 squares, etc, you get the pattern 3, 7, 15, … - what you should notice is that each number is one less than a power of 2. Thus, the number of grains on the first 5 squares is 2^5 - 1 = 31, and the number of grains on the first and squares is 2^n - 1.

In the case of a 64 square chessboard, then, you just need to calculate 2^64 - 1 - in other words, multiply 2 by itself 64 times, then subtract one.

The answer is a really big number - if your calculator has a power button, it may still not be able to calculate it. You can use a better calculator (windows calc will handle it, even!), or do it on paper fairly easily.

I won’t give the answer, since I’m hoping based on this primer you can figure it out for yourself.

Option 1: Do it on paper. You can multiply stuff by 2, right? Option 2: Use windows calc. Option 3: Find a site that has a built in calculator that handles large numbers. Option 4: Just write down “2^64 - 1” (2 with a superscript 64) as the answer.

That’s a sign of a calculator that can’t handle integers that big very well (there should be a number after the ‘e’ ). Try windows calc. :)

thank you I get it now I’ll be back in a bit im going to go figure it t

8,446,744,073,709,551,615

Did this problem too. There’s a mathematical formula on Wikipedia.

SOZ I cant do it my brain is on fire … what am I going to do