Lesson 17a: Subtracting 6, 7, 8 and 9 on an abacus
Level 2, Easy Street. Top bead up, bottom beads down.
What your child does, card by card
Taking away 6, 7, 8 and 9. Minus 5, and some more. PlayType opens the lesson: “To take away, move beads off the bar.”
7 − 6 = 1: 6 is 5 and 1. Take away 5, then 1. 7 appears on the beads, then the rod clears again. Here the hands lead: they show 7, 2 and 1, and a moment later the beads copy each one. Above, “−5: the top bead”, “−1: one bead” and “= 1” take turns to glow. Its words: “Read the beads: that is the answer.”
9 − 7 = 2: 7 is 5 and 2. Take away 5, then 2. The abacus makes 9, then clears. The labels “− 5 = 4” and “− 2 = 2” light up as each idea comes. “8 is 5 and 3. 9 is 5 and 4.” Any bead or finger may be tapped afterwards.
One finger takes away 6 to 9, on a real abacus. The pointer finger does both moves. First the pointer finger turns yellow on a drawn hand while the abacus moves. After that your child must work out 7 - 6 and 9 - 7, guided by a green ring and the finger’s name. Top bead up, then bottom beads down.
In Try it a green ring marks the next bead while your child works out 7 - 6, 9 - 7, 6 - 6, 9 - 8 and 9 - 9.
The tiny practice drops the ring: work out 9 - 6, 8 - 7, 8 - 6, 8 - 8 and 7 - 7, each round starting from its own number.
Copy me: the beads show 1, 2 and 3 and your child answers by tapping the drawn fingers, the hands window glowing.
Then the beads hide and the sums 7 - 6, 9 - 7 and 8 - 8 are done in the head, the answer shown on the fingers.
You're ready! Minus 6, 7, 8 and 9: the top bead and some more.
What this lesson trains
About five minutes and 18 answers. Altogether the child makes 24 bead moves (12 with the top bead, 12 with bottom beads). Clearing comes up 4 times. 9 is the top number here. Then 3 quick looks in your head.
Your child’s first moves: work out 7 - 6 and 9 - 7.
Fingers and hands
Below the abacus the drawn hands show zero and 1, 2, 3, 6, 7, 8 and 9 here, finger for bead.
On “7 − 6 = 1” 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 beads lead with 1, 2 and 3, and your child answers on the fingers: the reverse of making a number on the beads.
On “One finger takes away 6 to 9”, the pointer finger pulls bottom beads down and moves the top bead.
What PlayBuddy and PlayType say
PlayType: “To take away, move beads off the bar.”
PlayBuddy: “To take away six, take away five, then take away one.”
Stars
Three stars for up to 1 slip in 18 answers, two stars for up to 4.