Lesson 60: Abacus mixed friends: plus 7, 8 and 9
Level 5, Mix Mountain. The same mix as plus 6: the small part first, then the five.
What your child does, card by card
The mix: plus 7, plus 8 and plus 9. 7, 8 and 9 are five and some more. PlayBuddy opens the lesson: “First try the beads. Then the small friend. Then the big friend.”
+7 = +2 −5 +10: 7 is 5 and 2. The 2 first, then the 5. First the abacus shows the rule bead by bead (“+2: two beads up”, “−5: top bead off” and “+10: one ten on”). Next it is your child's turn: work out 6 + 7, 5 + 8 and 5 + 9, the ring marking the top bead before the friend.
First a reminder (“6 + 8, then 5 + 9”): the beads build 6, 9, 4, 14, 5, 9, 4 and 14, ring by ring, while your child watches. 8 is 5 and 3. 9 is 5 and 4.
Try it: your child works out 7 + 7, 6 + 8 and 15 + 9, with a green ring on the next bead to move.
Then a short practice without rings: work out 5 + 7, 6 + 9, 16 + 8, 4 + 8 and 5 + 9, each round starting from its own number.
In Copy me the drawn hand holds up 13, 14 and 12 in turn, and your child copies each one in beads.
In your head: the abacus is covered and your child works out 5 + 7, 6 + 8 and 5 + 9, showing each answer on the drawn fingers.
You're ready! Plus 7, 8 and 9: the small part, then the five.
What this lesson trains
About five minutes and 17 answers. Altogether the child makes 37 bead moves (9 with the top bead, 28 with bottom beads). Numbers reach 24, so the tens rod and the ones rod work. Then 3 quick looks in your head. Friends do 11 of the 11 sums, by +7 = +2 −5 +10, +8 = +3 −5 +10, +9 = +4 −5 +10, +9 = −1 +10 and +8 = −2 +10.
The first thing your child does: work out 7 + 7, 6 + 8 and 15 + 9.
Fingers and hands
Below the abacus the drawn hands show zero and 4, 5, 6, 7, 8, 9, 12, 13, 14, 15, 16 and 24 here, finger for bead: the left hand counts the tens, the right hand the ones.
+7 on the fingers: the right hand opens 2 fingers and folds the thumb, then the left hand opens one more finger for the ten (+2 −5 +10). +8 on the fingers: the right hand opens 3 fingers and folds the thumb, then the left hand opens one more finger for the ten (+3 −5 +10). +9 on the fingers: the right hand opens 4 fingers and folds the thumb, then the left hand opens one more finger for the ten (+4 −5 +10). +9 on the fingers: the right hand lets 1 go and the left hand opens one more finger for the ten (−1 +10). +8 on the fingers: the right hand lets 2 go and the left hand opens one more finger for the ten (−2 +10).
On “The mix: plus 7, plus 8 and plus 9” 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: 13, 14 and 12 appear on the hand first.
What PlayBuddy and PlayType say
PlayBuddy: “First try the beads. Then the small friend. Then the big friend.”
Stars
With 1 or fewer slips across the 17 answers your child earns three stars; 4 or fewer, two.