Lesson 105: Faster flash sums: abacus mental math
Level 9, Mind Castle. The numbers come faster now. Stay calm, picture the beads, and add each one.
What your child does, card by card
Faster flashes. Each number stays a shorter time. PlayType opens the lesson: “The numbers come faster now. Stay calm and watch.”
Try it: your child works out the columns 5 + 4 + 3 and 7 + 1 + 6 + 2, with a green ring on the next bead to move.
Flash sums in your head: the abacus is covered and the numbers appear one at a time, 1.1 seconds each (4 + 3 + 2 and 6 + 2 + 1 + 5); your child adds them in the head and picks the total from 9, 12 and 14.
Flash sums in your head: the abacus is covered and the numbers appear one at a time, 0.75 seconds each (5 + 4 + 3, 7 + 1 + 6 + 2, 8 + 5 - 3 + 4 and 2 + 9 + 3 + 6); your child adds them in the head and picks the total from 12, 14, 16 and 20.
You're ready! Faster flashes, the same calm adding.
What this lesson trains
11 answers, roughly five minutes: 10 moves of the beads, 3 of them with the top bead and 7 with bottom beads. Up to 16, read and set from the left. Then 2 quick looks in your head. The friend rules here: +3 = −7 +10, +6 = +1 −5 +10 and +2 = +5 −3, used in 3 of 5 sums.
It starts with doing: work out the columns 5 + 4 + 3 and 7 + 1 + 6 + 2.
The sum sheet
The lower window shows the column as a child would write it on paper: one number under another, the current line in yellow, ticks on the lines done. The abacus carries the running total from line to line.
What PlayBuddy and PlayType say
PlayType: “The numbers come faster now. Stay calm and watch.”
Stars
11 answers: 1 slip still gives three stars; up to 2, two stars.