Big Friends Bridge — Lesson 51: Big friends: minus 7 and minus 6

What your child does, card by card

Big friends: minus 7 and minus 6. 7 and 3 make 10. 6 and 4 make 10. PlayType opens the lesson: “Same trick, new friend.”

17 − 9 = 8: taking a ten is 1 too many. Give 1 back. 17 appears on the beads, then the rod clears again. Here the hands lead: they show 17, 7 and 8, and a moment later the beads copy each one. On the card, “−10” and “1 back = 8” light up one by one. Then the card invites a touch: “The trick of lesson 48.”

11 − 7: only 1 bead on the ones rod. Yellow marks the ones rod while the kids talk about it. The abacus makes 11, then clears. Each label lights in turn: “Start at 11” and “− 7? Only 1 one”. After the show, the child can touch: “7 will not come off. So take a ten!”

Minus 7: one ten off, 3 on: 10 is 7 and 3. Taking a ten is 3 too many. The beads act out the friend rule while “−10: one ten”, “+3: the big friend” and “−7 = −10 +3” light up; then your child must work out 11 - 7 and 15 - 7, a green ring on each bead in the friend's order.

Watch me: 10, 4, 15, 5 and 9 appear on the beads one move at a time, each bead ringed in green before it goes. 6 and 4 are big friends. The ten goes off. 4 beads come on.

Try it puts a green ring on each next bead; your child works out 10 - 7, 15 - 6 and 16 - 7.

A tiny practice with no ring: work out 10 - 6, 11 - 7, 18 - 7, 15 - 7 and 10 - 7, each round starting from its own number.

Copy me: the hand in the lower window shows 4, 8 and 9, one at a time, and your child makes the same number on the beads.

Then the beads hide and the sums 11 - 7, 10 - 6 and 15 - 7 are done in the head, the answer shown on the fingers.

You're ready! Minus 7: take a ten, give 3 back. Minus 6: take a ten, give 4 back.

What this lesson trains

About five minutes and 16 answers. Altogether the child makes 25 bead moves (3 with the top bead, 22 with bottom beads). The largest is 18: tens and ones. Then 3 quick looks in your head. Friends do 9 of the 10 sums, by −7 = −10 +3 and −6 = −10 +4.

It starts with doing: work out 10 - 7, 15 - 6 and 16 - 7.

Fingers and hands

Below the abacus the drawn hands show zero and 3, 4, 7, 8, 9, 10, 11, 15, 16, 17 and 18 here, finger for bead: the left hand counts the tens, the right hand the ones.

−7 on the fingers: the left hand closes one finger for the ten and the right hand shows 3 more (−10 +3). −6 on the fingers: the left hand closes one finger for the ten and the right hand shows 4 more (−10 +4).

On “17 − 9 = 8” 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 4, 8 and 9 and your child turns each into beads.

What PlayBuddy and PlayType say

PlayBuddy: “Taking ten is one too many. So one bead comes back!”

Stars

16 answers: 1 slip still gives three stars; up to 4, two stars.