Lesson 16: Abacus subtraction: minus 1 to 4
Level 2, Easy Street. Adding puts beads on. Taking away takes them off.
What your child does, card by card
Taking away bottom beads. Minus 1, 2, 3 or 4. PlayType opens the lesson: “To take away, move beads off the bar.”
4 − 1 = 3: start at 4. Move one bead down. The beads show 4 and go back to zero. On the card, “Start at 4”, “− 1 bead” and “= 3” light up one by one. Then the card invites a touch: “Read the beads: that is the answer.”
Close a finger to take away: 4 − 1: four fingers up. Close one. 3 appears on the beads, then the rod clears again. Here the hands lead: they show 3, 4 and 3, and a moment later the beads copy each one. Each label lights in turn: “Open = add” and “Close = take away”. After the show, the child can touch: “Tap a finger to try it.”
First a reminder (“4 − 3”): the beads build 4 and 1, ring by ring, while your child watches. Make 4. Then move 3 beads off the bar.
Try it: your child works out 4 - 1, 4 - 3, 3 - 1, 2 - 2 and 7 - 2, with a green ring on the next bead to move.
Then a short practice without rings: work out 4 - 1, 3 - 2, 9 - 3, 4 - 4 and 8 - 2, each round starting from its own number.
In Copy me the drawn hand holds up 3, 1 and 4 in turn, and your child copies each one in beads.
In your head: the abacus is covered and your child works out 3 - 1, 4 - 3 and 4 - 1, showing each answer on the drawn fingers.
You're ready! You can take away 1 to 4 with the bottom beads.
What this lesson trains
About five minutes and 16 answers. Altogether the child makes 13 bead moves (0 with the top bead, 13 with bottom beads). Clearing comes up 2 times. Nothing goes past 9. Then 3 quick looks in your head.
It starts with doing: work out 4 - 1, 4 - 3, 3 - 1, 2 - 2 and 7 - 2.
Fingers and hands
Below the abacus the drawn hands show zero and 1, 2, 3, 4, 5, 6, 7, 8 and 9 here, finger for bead.
On “Close a finger to take away” the hands move first and the beads follow, so your child sees that a finger and a bead move together: open a finger and a bead goes to the bar, close it and the bead goes back.
In Copy me the hand leads with 3, 1 and 4 and your child turns each into beads.
What PlayBuddy and PlayType say
PlayType: “To take away, move beads off the bar.”
Stars
16 answers: 1 slip still gives three stars; up to 4, two stars.