You Can’t Beat God Giving By R.W. Schwambach
Young Achievers Mental Maths 4
The Mental Maths- Young Achievers series: is a set of six books for primary schools, designed to help children master their command over mathematical concepts.
Mental math is a group of skills that allow people to do math “in their head” without using pencil and paper or a calculator. One of these skills is remembering math facts, like 8 × 5 = 40. Other skills include rounding numbers and estimating calculations.