Explain how useing basic facts can you find 10×20×30×40 mentally.

You just do 1x2x3x4 and that equals 24 so now you have 24 and then you add 4 zeros because their are 4 zeros in the equation so then the final answer is 240000 hope it helps:)❤️

Multiply 1 x 2 then add the two zeros to that answer the multiply 3 x 4 and add the two zeros to the end and then multiply the answer from 1 x 2 ( with the two zeros) and 3 x 4 (with the two zeros) and that should be your answer . :)