Big Friends Bridge — Lesson 45: Big friends: plus 4 and plus 3
Big friends: plus 2 and plus 1 →Lesson 45: Big friends plus 4 and plus 3 on an abacus
Level 4, Big Friends Bridge. When the small friend cannot help, the big friend does.
What your child does, card by card
Big friends: plus 4 and plus 3. 4 and 6 make 10. 3 and 7 make 10. PlayType opens the lesson: “Small numbers have big friends too.”
3 + 4 = 7: the top bead is free. Add 5, take 1 back. The abacus makes 3, then clears. Here the hands lead: they show 3, 8 and 7, and a moment later the beads copy each one. On the card, “+5” and “1 back = 7” light up one by one. Then the card invites a touch: “The small friend, from lesson 25.”
7 + 4: only 2 beads free. And the top bead is down. The ones rod is outlined in yellow while the kids explain. The beads show 7 and go back to zero. Each label lights in turn: “Start at 7” and “+ 4? Only 2 fit”. After the show, the child can touch: “No small friend here. So add a ten!”
Plus 4: 6 off, one ten on: 10 is 4 and 6. So a ten is 6 too many. The beads act out the friend rule while “−6: the big friend”, “+10: one ten” and “+4 = −6 +10” light up; then your child must work out 7 + 4 and 9 + 4, a green ring on each bead in the friend's order.
Watch me: 8, 1 and 11 appear on the beads one move at a time, each bead ringed in green before it goes. 10 is 3 and 7. Take 7 off, then one ten on.
Try it puts a green ring on each next bead; your child works out 6 + 4, 8 + 3 and 9 + 3.
A tiny practice with no ring: work out 7 + 4, 3 + 4, 8 + 4, 7 + 3 and 9 + 4, each round starting from its own number.
Copy me: the hand in the lower window shows 11, 13 and 7, one at a time, and your child makes the same number on the beads.
Then the beads hide and the sums 6 + 4, 8 + 3 and 9 + 4 are done in the head, the answer shown on the fingers.
You're ready! Plus 4: take 6 off. Plus 3: take 7 off. Then add a ten.
What this lesson trains
16 answers in about five minutes. The tasks take 35 bead moves in all: 11 with a top bead and 24 with bottom beads. Up to 13, read and set from the left. Then 3 quick looks in your head. Friends do 10 of the 10 sums, by +4 = −6 +10, +3 = −7 +10 and +4 = +5 −1.
Your child’s first moves: work out 6 + 4, 8 + 3 and 9 + 3.
Fingers and hands
Below the abacus the drawn hands show zero and 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13 here, finger for bead: the left hand counts the tens, the right hand the ones.
+4 on the fingers: the thumb opens and one finger closes (+5 −1).
+4 on the fingers: the right hand lets 6 go and the left hand opens one more finger for the ten (−6 +10). +3 on the fingers: the right hand lets 7 go and the left hand opens one more finger for the ten (−7 +10).
On “3 + 4 = 7” 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 (11, 13 and 7); the beads answer.
What PlayBuddy and PlayType say
PlayType: “Small numbers have big friends too.”
PlayBuddy: “Five is one too many. So one bead goes back!”
PlayBuddy: “No room on this rod. Ask the big friend.”
Stars
Three stars for up to 1 slip in 16 answers, two stars for up to 4.