Mix Mountain — Lesson 64: Mix practice: taking away
When the ten needs a small friend →Lesson 64: Abacus mixed friends subtraction practice
Level 5, Mix Mountain. Every kind of taking away. Fill the bead jar.
What your child does, card by card
Mix practice: taking away. Practice day! PlayBuddy opens the lesson: “Practice time. Let's get quicker and better.”
First a reminder (“13 − 6: ten off, top bead on, one down”): the beads build 13, 3, 8 and 7, ring by ring, while your child watches. 6 is 5 and 1. The 5 first, then the 1.
Try it: your child works out 12 - 6 and 13 - 7, with a green ring on the next bead to move.
Ten beads to go: a mission of 10 tasks with a bead jar that fills with every right answer. Your child must work out 11 - 6, 14 - 8, 12 - 7, 14 - 9, 13 - 6, 12 - 9, 7 - 4, 14 - 7, 22 - 6 and 23 - 8.
Copy me: the beads show 7, 6 and 15 and your child answers by tapping the drawn fingers, the hands window glowing.
Then the beads hide and the sums 13 - 6, 12 - 7 and 14 - 9 are done in the head, the answer shown on the fingers.
Jar full! All the taking away, with every friend.
What this lesson trains
18 answers, roughly five minutes: 34 moves of the beads, 11 of them with the top bead and 23 with bottom beads. The largest is 23: tens and ones. Then 3 quick looks in your head. 12 of the 12 sums need a friend (“−6 = −10 +5 −1”, “−7 = −10 +5 −2”, “−8 = −10 +5 −3”, “−9 = −10 +5 −4”, “−9 = −10 +1” and “−4 = −5 +1”); the others use free beads.
It starts with doing: work out 12 - 6 and 13 - 7.
Fingers and hands
Below the abacus the drawn hands show zero and 3, 5, 6, 7, 11, 12, 13, 14, 15, 16, 22 and 23 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).
−6 on the fingers: the left hand closes one finger for the ten, then the right hand puts the thumb out and closes one finger (−10 +5 −1). −7 on the fingers: the left hand closes one finger for the ten, then the right hand puts the thumb out and closes 2 fingers (−10 +5 −2). −8 on the fingers: the left hand closes one finger for the ten, then the right hand puts the thumb out and closes 3 fingers (−10 +5 −3). −9 on the fingers: the left hand closes one finger for the ten, then the right hand puts the thumb out and closes 4 fingers (−10 +5 −4). −9 on the fingers: the left hand closes one finger for the ten and the right hand shows 1 more (−10 +1).
In Copy me the beads lead with 7, 6 and 15, and your child answers on the fingers: the reverse of making a number on the beads.
What PlayBuddy and PlayType say
PlayBuddy: “First try the beads. Then the small friend. Then the big friend.”
Stars
18 answers: 1 slip still gives three stars; up to 4, two stars.