Multiply decimals fast: multiply as whole numbers, then place the point by adding up the decimal places.
Preview · progress not saved — Chapter 1 is free
Places in the product = places in the first number + places in the second.
Multiplying decimals is multiplying their fractions.
Using the rule with a known product, then from scratch.
Problem 1. Given , write . (Math Talk, Textbook p. 71)
Multiply as whole numbers, then count places.
Find products by counting tenths and hundredths.
Figure it Out, Textbook p. 73, Q1. Recall that a tenth is 0.1 and a hundredth is 0.01.
(a) 6 × 4 tenths = 24 tenths =
(b) 7 × 0.3 = 7 × 3 tenths = tenths =
(c) 9 × 5 hundredths = hundredths =
Decimal products from the exercises.
(Textbook p. 73, Q2a)
Write six decimal products from one known product.
Figure it Out, Textbook p. 73, Q8. Given 18 × 12 = 216:
(a) 18 × 1.2 =
(b) 18 × 0.12 =
(c) 1.8 × 1.2 =
(d) 0.18 × 0.12 =
(e) 0.018 × 0.012 =
(f) 1.8 × 12 =
The products less than 1 are (d) and ().