How much is 1x2 plus 2x3 plus 3x4 plus &; -; -; -; -; -; -; -; -; -; -; -; plus 99x100? There should be a calculation process

How much is 1x2 plus 2x3 plus 3x4 plus &; -; -; -; -; -; -; -; -; -; -; -; plus 99x100? There should be a calculation process

1x2 plus 2x3 plus 3x4 plus &; -; -; -; -; -; -; -; -; -; -; -; plus 99x100
=1*(1+1)+2*(2+1)+3*(3+1)+...+99*(99+1)
=1^2+2^2+3^2+...+99^2+(1+2+3+...+99)
=99*(99+1)(99*2+1)/6+99(99+1)/2
Do it yourself

It is known that a times b equals 380. If a times 3 and B is constant, what is the product? If a is constant and B is divided by 5, what is the product?

It is known that a times b equals 380. If a times 3 and B is constant, then the product is (1140)
If a is constant and B is divided by 5, then the product is (76)

Given AXB = 400, if B is constant and a is multiplied by 3, then the product is (). If a is constant and B is divided by 5, then the product is ()

Given AXB = 400, if B is constant and a is multiplied by 3, then the product is (1200). If a is constant and B is divided by 5, then the product is (80)

Given AXB = 400, if B is constant and a is multiplied by 3, what is the product? If a is constant and B is divided by 5, what is the product

A: AXB = 400
Ax3xB=400x3=1200
AXB divided by 5 = 400 divided by 5 = 80