Question

вычислите произведения удобным способом 30*21

Answer 1

30*21=3*10*21=21*3*10=63*10=630

Answer 2

30 * 21 = 30 * 20 + 30 * 1 = 600 + 30 = 630
30 * 21 = 3 * 21 * 10 = 63 * 10 = 630