Easy Street — Lesson 20: Adding tens and ones

What your child does, card by card

Adding tens and ones. 23 + 51, and more. PlayBuddy opens the lesson: “Big numbers have tens and ones. Let's add both.”

23 + 51 = 74: add 5 tens, then 1 one. Yellow marks the tens rod and the ones rod while the kids talk about them. The abacus makes 23, then clears. Here the hands lead: they show 73 and 74, and a moment later the beads copy each one. Above, “Start at 23”, “+ 50 = 73” and “+ 1 = 74” take turns to glow. Its words: “We say fifty-one: tens first. Add them first.”

Watch me: 12, 42 and 47 appear on the beads one move at a time, each bead ringed in green before it goes. 3 tens first, then 5 ones.

Try it puts a green ring on each next bead; your child works out 23 + 51, 12 + 35, 30 + 15 and 15 + 32.

A tiny practice with no ring: work out 60 + 21, 52 + 16, 31 + 63 and 21 + 11, each round starting from its own number.

In Copy me the drawn hand holds up 74, 47 and 55 in turn, and your child copies each one in beads.

In your head: the abacus is covered and your child works out 23 + 51, 12 + 35 and 25 + 52, showing each answer on the drawn fingers.

You're ready! You can add tens and ones.

What this lesson trains

14 answers, roughly five minutes: 26 moves of the beads, 9 of them with the top bead and 17 with bottom beads. Up to 94, read and set from the left. Then 3 quick looks in your head.

Your child’s first moves: work out 23 + 51, 12 + 35, 30 + 15 and 15 + 32.

Fingers and hands

Below the abacus the drawn hands show zero and 12, 15, 20, 21, 23, 30, 31, 32, 45, 47, 52, 55, 60, 68, 73, 74, 81 and 94 here, finger for bead: the left hand counts the tens, the right hand the ones.

On “23 + 51 = 74” the hands move first and the beads follow, so your child sees that a finger and a bead move together: open a finger and a bead goes to the bar, close it and the bead goes back.

Copy me turns it round: 74, 47 and 55 appear on the hand first.

What PlayBuddy and PlayType say

PlayBuddy: “Big numbers have tens and ones. Let's add both.”

Stars

Three stars for up to 1 slip in 14 answers, two stars for up to 3.