Multiply Polynomials · Exercise 71

Mental math You can use binomial multiplication to multiply numbers without a calculator. Say you need to multiply $13$ times $15.$ Think of $13$ as $10+3$ and $15$ as $10+5.$

ⓐ Multiply $\left(10+3\right)\left(10+5\right)$ by the FOIL method.
ⓑ Multiply $13\cdot 15$ without using a calculator.
ⓒ Which way is easier for you? Why?

This is an open-ended exercise: its source gives no single answer.

OpenStax, Prealgebra 2e · §10.3 Multiply Polynomials · Exercise 71