Column Tower — Lesson 72: Columns of four and five numbers
One-digit column practice →Lesson 72: Abacus column sums: four and five numbers
Level 6, Column Tower. Four or five numbers, one line at a time.
What your child does, card by card
Columns of four and five numbers. A taller tower, the same way. PlayBuddy opens the lesson: “One line at a time, top to bottom.”
Watch me: 4, 1, 11, 1, 9, 5 and 15 appear on the beads one move at a time, each bead ringed in green before it goes. Read the sign on every line: plus or minus?
Try it puts a green ring on each next bead; your child works out the columns 4 + 7 - 2 + 6 and 8 + 5 - 6 + 9 - 3.
A tiny practice with no ring: work out the columns 6 + 6 - 4 + 7 and 9 - 5 + 8 + 3 - 6, each round starting from its own number.
In your head: the abacus is covered and your child works out 2 + 3 + 1 + 2, 9 - 3 - 2 + 1 and 4 + 4 + 1 - 3, picking each answer from 5, 6 and 8.
You're ready! Four and five lines, one at a time.
What this lesson trains
17 answers, roughly five minutes: 31 moves of the beads, 8 of them with the top bead and 23 with bottom beads. The largest is 16: tens and ones. Then 3 quick looks in your head. Friends do 13 of the 14 sums, by +7 = −3 +10, −2 = −10 +8, +6 = −4 +10, +5 = −5 +10, −6 = −10 +5 −1, +9 = −1 +10, −3 = −5 +2, +6 = +1 −5 +10, −4 = −10 +6, +8 = −2 +10, +3 = +5 −2 and −6 = −10 +4.
Your child’s first moves: work out the columns 4 + 7 - 2 + 6 and 8 + 5 - 6 + 9 - 3.
The sum sheet
Below the abacus a sum sheet replaces the hands: it writes the column out, lights the line your child is on and ticks each line done; the total appears after the last line. The beads hold the running total the whole way down.
What PlayBuddy and PlayType say
PlayBuddy: “One line at a time, top to bottom.”
Stars
Three stars for up to 1 slip in 17 answers, two stars for up to 4.