Big Friends Bridge — Lesson 49: Big friends: minus 8
Minus 9 and minus 8 practice →Lesson 49: Big friends minus 8 on an abacus
Level 4, Big Friends Bridge. Minus 8: take a ten, give 2 back.
What your child does, card by card
Big friends: minus 8. 8 and 2 make 10. PlayType opens the lesson: “Same trick, new friend.”
13 − 9 = 4: taking a ten is 1 too many. Give 1 back. The abacus makes 13, then clears. Here the hands lead: they show 13, 3 and 4, and a moment later the beads copy each one. Each label lights in turn: “−10” and “1 back = 4”. After the show, the child can touch: “The trick of lesson 48.”
11 − 8: only 1 bead on the ones rod. The ones rod is outlined in yellow while the kids explain. The beads show 11 and go back to zero. “Start at 11” and “− 8? Only 1 one” glow on the card in step with the beads. The card ends on a touch: “8 will not come off. So take a ten!”
Minus 8: one ten off, 2 on: 10 is 8 and 2. Taking a ten is 2 too many. The beads act out the friend rule while “−10: one ten”, “+2: the big friend” and “−8 = −10 +2” light up; then your child must work out 11 - 8 and 16 - 8, a green ring on each bead in the friend's order.
In Try it a green ring marks the next bead while your child works out 10 - 8, 12 - 8 and 15 - 8.
The tiny practice drops the ring: work out 17 - 8, 11 - 8, 18 - 8, 16 - 8 and 10 - 8, each round starting from its own number.
In Copy me the drawn hand holds up 3, 8 and 2 in turn, and your child copies each one in beads.
In your head: the abacus is covered and your child works out 11 - 8, 15 - 8 and 12 - 8, showing each answer on the drawn fingers.
You're ready! Not enough ones to take 8? Take a ten, give 2 back.
What this lesson trains
About five minutes and 16 answers. Altogether the child makes 24 bead moves (2 with the top bead, 22 with bottom beads). Up to 18, read and set from the left. Then 3 quick looks in your head. Friends do 9 of the 10 sums, by −8 = −10 +2.
Your child’s first moves: work out 10 - 8, 12 - 8 and 15 - 8.
Fingers and hands
Below the abacus the drawn hands show zero and 2, 3, 4, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17 and 18 here, finger for bead: the left hand counts the tens, the right hand the ones.
−8 on the fingers: the left hand closes one finger for the ten and the right hand shows 2 more (−10 +2).
On “13 − 9 = 4” 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 (3, 8 and 2); the beads answer.
What PlayBuddy and PlayType say
PlayBuddy: “Taking ten is one too many. So one bead comes back!”
Stars
Three stars for up to 1 slip in 16 answers, two stars for up to 4.