Big Friends Bridge — Lesson 53: Big friends: minus 4 and minus 3

What your child does, card by card

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

7 − 4 = 3: the top bead is on the bar. Take 5, give 1 back. 7 appears on the beads, then the rod clears again. Here the hands lead: they show 7, 2 and 3, and a moment later the beads copy each one. Above, “−5” and “1 back = 3” take turns to glow. Its words: “The small friend, from lesson 32.”

12 − 4: only 2 ones. No top bead on the bar. Yellow marks the ones rod while the kids talk about it. The abacus makes 12, then clears. The labels “Start at 12” and “− 4? Only 2 ones” light up as each idea comes. “No small friend here. So take a ten!” Any bead or finger may be tapped afterwards.

Minus 4: one ten off, 6 on: 10 is 4 and 6. Taking a ten is 6 too many. First the abacus shows the rule bead by bead (“−10: one ten”, “+6: the big friend” and “−4 = −10 +6”). Next it is your child's turn: work out 12 - 4 and 10 - 4, the ring marking the top bead before the friend.

First a reminder (“11 − 3”): the beads build 11, 1 and 8, ring by ring, while your child watches. 10 is 3 and 7. One ten off, then 7 on.

Try it: your child works out 11 - 3, 13 - 4 and 12 - 3, with a green ring on the next bead to move.

Then a short practice without rings: work out 12 - 4, 16 - 4, 11 - 4, 10 - 3, 12 - 3 and 13 - 4, each round starting from its own number.

Copy me: the hand in the lower window shows 8, 6 and 12, one at a time, and your child makes the same number on the beads.

Then the beads hide and the sums 12 - 4, 11 - 3 and 10 - 4 are done in the head, the answer shown on the fingers.

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

What this lesson trains

About five minutes and 17 answers. Altogether the child makes 38 bead moves (13 with the top bead, 25 with bottom beads). The largest is 16: tens and ones. Then 3 quick looks in your head. 11 of the 11 sums need a friend (“−4 = −10 +6”, “−3 = −10 +7” and “−4 = −5 +1”); the others use free beads.

It starts with doing: work out 11 - 3, 13 - 4 and 12 - 3.

Fingers and hands

Below the abacus the drawn hands show zero and 2, 3, 6, 7, 8, 9, 10, 11, 12, 13 and 16 here, finger for bead: the left hand counts the tens, the right hand the ones.

−4 on the fingers: the thumb closes and one finger opens (−5 +1).

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

On “7 − 4 = 3” 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.

Copy me turns it round: 8, 6 and 12 appear on the hand first.

What PlayBuddy and PlayType say

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

Stars

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