I am doing some repetition of complex numbers and I got to this question:
Calculate the absolute value of $z=(10+5i)(1+10i)(4+2i)(5+2i)$
My approach has been to first multiply the imaginary numbers and then I get: $z = -2530 + 960i$
I am not supposed to use a calculator so this is not an easy number to calculate the absolute value of. There must be an easier (smarter) way of doing this?