Big Friends Bridge — Lesson 55: Big friends: all the taking away
Big friends on the tens rod →Lesson 55: Abacus big friends subtraction practice
Level 4, Big Friends Bridge. Every big friend, from minus 9 to minus 1. Then beat your best time!
What your child does, card by card
Big friends: all the taking away. Practice day! PlayBuddy opens the lesson: “Practice time. Let's get quicker and better.”
Watch me: 19, 15, 10, 11, 1 and 7 appear on the beads one move at a time, each bead ringed in green before it goes. Beads there? Take them. Top bead there? Small friend. Neither? Big friend.
Try it puts a green ring on each next bead; your child works out 16 - 9, 14 - 5 and 7 - 4.
Fast sums: a mission of 10 tasks with a clock against your child’s own best time. Your child must work out 12 - 9, 11 - 8, 15 - 7, 10 - 6, 13 - 5, 7 - 4, 12 - 4, 11 - 3, 18 - 6 and 10 - 1.
Copy me: the beads show 18, 3 and 12 and your child answers by tapping the drawn fingers, the hands window glowing.
Then the beads hide and the sums 13 - 5, 12 - 9 and 11 - 4 are done in the head, the answer shown on the fingers.
You're ready! You can take away through ten with every big friend.
What this lesson trains
19 answers, roughly five minutes: 29 moves of the beads, 8 of them with the top bead and 21 with bottom beads. The largest is 18: tens and ones. Then 3 quick looks in your head. Friends do 12 of the 13 sums, by −9 = −10 +1, −5 = −10 +5, −4 = −5 +1, −8 = −10 +2, −7 = −10 +3, −6 = −10 +4, −4 = −10 +6, −3 = −10 +7 and −1 = −10 +9.
It starts with doing: work out 16 - 9, 14 - 5 and 7 - 4.
Fingers and hands
Below the abacus the drawn hands show zero and 3, 4, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and 18 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).
−9 on the fingers: the left hand closes one finger for the ten and the right hand shows 1 more (−10 +1). −5 on the fingers: the left hand closes one finger for the ten and the right hand shows 5 more (−10 +5). −8 on the fingers: the left hand closes one finger for the ten and the right hand shows 2 more (−10 +2). −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). −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). −1 on the fingers: the left hand closes one finger for the ten and the right hand shows 9 more (−10 +9).
In Copy me the beads lead with 18, 3 and 12, 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
19 answers: 1 slip still gives three stars; up to 4, two stars.