Mix Mountain — Lesson 62: The mix: minus 6
The mix: minus 7, minus 8 and minus 9 →Lesson 62: Abacus mixed friends: minus 6
Level 5, Mix Mountain. What if no top bead is on the bar? Two moves you know do it.
What your child does, card by card
The mix: minus 6. Take away 6: take 5 and take 1. PlayType opens the lesson: “Now let's try a harder one.”
7 − 6 = 1: minus 6 is minus 5 and minus 1. The abacus makes 7, then clears. Here the hands lead: they show 7, 2 and 1, and a moment later the beads copy each one. Each label lights in turn: “−5: the top bead”, “−1: one bead” and “= 1”. After the show, the child can touch: “Top bead up, then one bead down.”
12 − 5 = 7: no top bead on the bar? Borrow a ten. The beads show 12 and go back to zero. Here the hands lead: they show 12, 2 and 7, and a moment later the beads copy each one. “−10: one ten off”, “+5: top bead on” and “= 7” glow on the card in step with the beads. The card ends on a touch: “Then the top bead comes on.”
12 − 6: the 5 first: there is no top bead to take. A yellow line goes round the top beads, the bottom beads and the tens rod as the kids name them. 12 appears on the beads, then the rod clears again. Here the hands lead: they show 12, and a moment later the beads copy it. Above, “Start at 12”, “−5: no top bead here” and “−1: a bead is there” take turns to glow. Its words: “So borrow a ten, like 12 − 5.”
−6 = −10 +5 −1: the 5 first, with a borrowed ten. Then the 1. On this card “−10: one ten”, “+5: the top bead” and “−1: one bead” glow in turn as the beads move. Your child copies the order to work out 12 - 6 and 14 - 6.
Try it: your child works out 11 - 6, 13 - 6 and 21 - 6, with a green ring on the next bead to move.
Then a short practice without rings: work out 14 - 6, 10 - 6, 12 - 6, 9 - 6 and 23 - 6, each round starting from its own number.
In Copy me the drawn hand holds up 6, 8 and 5 in turn, and your child copies each one in beads.
In your head: the abacus is covered and your child works out 12 - 6, 14 - 6 and 11 - 6, showing each answer on the drawn fingers.
You're ready! Minus 6: one ten off, top bead on, one bead down.
What this lesson trains
16 answers, roughly five minutes: 33 moves of the beads, 12 of them with the top bead and 21 with bottom beads. Up to 23, read and set from the left. Then 3 quick looks in your head. 9 of the 10 sums need a big friend (“−6 = −10 +5 −1” and “−6 = −10 +4”); the others use free beads.
It starts with doing: work out 11 - 6, 13 - 6 and 21 - 6.
Fingers and hands
Below the abacus the drawn hands show zero and 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 21 and 23 here, finger for bead: the left hand counts the tens, the right hand the ones.
−6 on the fingers: the left hand closes one finger for the ten, then the right hand puts the thumb out and closes one finger (−10 +5 −1). −6 on the fingers: the left hand closes one finger for the ten and the right hand shows 4 more (−10 +4).
On “The mix: minus 6” 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 (6, 8 and 5); the beads answer.
What PlayBuddy and PlayType say
PlayBuddy: “To take away six, take away five, then take away one.”
PlayBuddy: “One ten off, big friend on.”
PlayType: “Now the mix, going backward. Borrow a ten first.”
Stars
16 answers: 1 slip still gives three stars; up to 4, two stars.