how do you make four 8s into 640??

does it have to be four?

8 * 8 * 10 = 640

I don't know if you can use the ten.

8/8 * 8 * 8 * 10 = 640

To make four 8s into 640, you can use various mathematical operations such as addition, subtraction, multiplication, and division. Here's one possible solution:

1. Start with the number 8: 8
2. Multiply the two 8s together: 8 x 8 = 64
3. Multiply the previous result (64) by another 8: 64 x 8 = 512
4. Divide the final result (512) by the remaining 8: 512 ÷ 8 = 64
5. Multiply the last result (64) by 10 to get 640: 64 x 10 = 640

So, the sequence of operations is 8 x 8 x 8 ÷ 8 x 10 = 640.