Here’s a game your students play using calculators–but that will teach them to have a stronger sense of decimal multiplication. (Like the last game I shared, this comes from the book Success from the Start.)
Split students into two teams, and start them off with a “target,” a range of numbers, and the “ball,” a single number.
The first team guesses a number; you multiply the ball by this number. If the result is within the target, the team wins. If not, the product becomes the new ball, and play goes to the other team. Teams go back and forth until they hit the target.
For example, we might set a target of 770 – 800, and a ball of 14.
Team 1 guesses 80. 14 x 80 = 1120. That’s too big, so 1120 becomes the new ball.
Team 2 guesses 0.8. 1120 x 0.8 = 896. That’s still too big.
Team 1 guesses 0.75. 896 x 0.75 = 672. That’s too small!
Team 2 guesses 1.1. 672 x 1.1 = 739.2. That’s also too small — though we’re getting close!
Team 1 guesses 1.05. 739.2 x 1.05 = 776.16. Team 1 wins!
This game, like most, can be adapted many ways. You can vary the target range, or vary the operatoin that students use. You can emphasize good calculator habits, as well as keeping track of work. Try it out!