How can you use 4x7 to find 8x7?
4 x 7 is 28, and 8 x 7 is 56. You can use 4 x 7 to find 8 x 7 by multiplying that first and doubling that quotient.
Half of 56 is 28, therefore doubling that allows us to find the quotient of 8 x 7.
You can use it because if you multiply 4x7, the answer is 28 and if you multiply 8x7 it is 56 and 28 is half of 56. Hope that helped!