Lesson 7a: Teen numbers on an abacus: 11 to 20
Level 1, Bead Village. Keep the ten. Count on with the ones rod.
What your child does, card by card
Counting on: 11 to 20. After 10 comes 11.
11, 12, 13, 14: the ten stays. The ones rod counts. A yellow line goes round the tens rod as the kids name it. 10 appears on the beads, then the rod clears again. The labels “11”, “12”, “13” and “14” light up as each idea comes. “Look under the rods: 1 and 1 is eleven.” Any bead or finger may be tapped afterwards.
15 to 19: the top bead is 5. Ten and five is 15. Yellow marks the ones rod while the kids talk about it. The abacus makes 14, then clears. Here the hands lead: they show 15, and a moment later the beads copy it. On the card, “15”, “16”, “17”, “18” and “19” light up one by one. Then the card invites a touch: “Just like 5, 6, 7, 8, 9.”
The swap again: the ones rod is full. One more ten! The ones rod and the tens rod are outlined in yellow while the kids explain. The beads show 19 and go back to zero. Here the hands lead: they show 19 and 20, and a moment later the beads copy each one. Each label lights in turn: “Full at 19” and “20 = 2 tens”. After the show, the child can touch: “Two beads on the tens rod: 20.”
28, 29, 30: the abacus makes 28, 29 and 30 by itself, a green ring on each bead just before it moves, and the hands copy. It happens at every 9.
In Try it a green ring marks the next bead while your child makes 10, 11, 12, 13, 14 and 15, changing the beads from one number to the next.
Try it puts a green ring on each next bead; your child goes from 15 to 16, makes 17, makes 18, makes 19 and makes 20, changing the beads from one number to the next.
Copy me: the hand in the lower window shows 11, 15, 19 and 20, one at a time, and your child makes the same number on the beads.
In your head: the beads flash 12, 15 and 20, one at a time, for 2 seconds each and hide; your child shows each number on the drawn fingers, then sees the beads again.
You're ready! You can count from 0 to 20, and on to 99.
What this lesson trains
18 answers in about five minutes. The tasks take 22 bead moves in all: 4 with a top bead and 18 with bottom beads. The largest is 20: tens and ones. Then 3 quick looks in your head.
The first thing your child does: make 10, 11, 12, 13, 14 and 15.
Fingers and hands
Below the abacus the drawn hands show zero and 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 here, finger for bead: the left hand counts the tens, the right hand the ones.
On “Counting on: 11 to 20” 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.
The fingers lead in Copy me (11, 15, 19 and 20); the beads answer.
What PlayBuddy and PlayType say
PlayBuddy: “Five and one is six. Five and two is seven.”
PlayBuddy: “Seven, eight, nine. Every bead is on the bar. This rod is full!”
PlayType: “One more? There is no room! So the nine beads go back, and one bead goes up on the next rod.”
Stars
With 1 or fewer slips across the 18 answers your child earns three stars; 4 or fewer, two.