Column Tower — Lesson 75: Two-digit column practice

What your child does, card by card

Two-digit column practice. Practice day! PlayBuddy opens the lesson: “Practice time. Let's get quicker and better.”

Watch me: 45, 95, 65, 67, 62, 72, 62, 52, 57 and 56 appear on the beads one move at a time, each bead ringed in green before it goes. Tens first, then ones, on every line.

Try it puts a green ring on each next bead; your child works out the column 38 + 24 - 19.

Ten beads to go: a mission of 10 tasks with a bead jar that fills with every right answer. Your child must work out the columns 12 + 34 + 25, 76 - 48 + 15, 53 + 29 - 37, 64 - 27 + 38 and 89 - 45 - 26.

In your head: the abacus is covered and your child works out 10 + 20 + 30, 70 - 30 - 10 and 40 + 40 - 20, picking each answer from 30, 60 and 70.

Jar full! Two-digit columns, a jar full.

What this lesson trains

About five minutes and 15 answers. Altogether the child makes 47 bead moves (16 with the top bead, 31 with bottom beads). Numbers reach 89, so the tens rod and the ones rod work. Then 3 quick looks in your head. Friends do 12 of the 12 sums, by +2 = +5 −3, +4 = −6 +10, −9 = −10 +1, +4 = +5 −1, +5 = −5 +10, −4 = −5 +1, −8 = −10 +2, +9 = −1 +10, −7 = −10 +5 −2, −2 = −5 +3, +3 = +5 −2, +8 = −2 +10 and −6 = −10 +5 −1.

The first thing your child does: work out the column 38 + 24 - 19.

The sum sheet

In Column Tower the lower window is a sum sheet instead of the hands: the column written out one line under another, the line being worked in yellow, the lines done ticked, and the total once the last line is in. The beads keep the running total, so the abacus is never cleared in the middle of a column.

What PlayBuddy and PlayType say

PlayBuddy: “Practice time. Let's get quicker and better.”

PlayBuddy: “Click Let's Begin, or press Enter!”

PlayType: “First the tens, and then the ones.”

PlayType: “Now do it in your head.”

Stars

With 1 or fewer slips across the 15 answers your child earns three stars; 3 or fewer, two.