Take three hands-up answers, not open call-outs. Give five seconds of quiet think-time first. Do not confirm or correct yet — you want to hear whether pupils think in fractions (a quarter) or jump straight to a percentage (25%). Both are the target of the lesson; hold them both up as worth exploring.

The move the whole lesson rests on: count the parts and add before you write any fraction. Count aloud each time so the whole is visible first.

1:3 — count 1 + 3 = 4 parts, so filled bar is 1/4 = 25%, empty bar 3/4 = 75%. After the reveal, turn-and-name: what is the empty part?

2:3 — count 2 + 3 = 5 parts, so filled 2/5 = 40%, empty 3/5 = 60%. The trap is reading 2:3 as two thirds; the bottom number is always the total number of parts, here 5. Ask before the readout confirms.

3:7 — before revealing, take a hands-up prediction: which part is bigger, more or less than half? Turn-and-name, then two or three predictions. Then count 3 + 7 = 10 parts, filled 3/10 = 30%, empty 7/10 = 70%.

Land the point every time: filled + empty = 100%. Revoice any pupil who says the two parts add back to the whole — that is the reasoning to lock in.

If the interactive fails, draw a ten-square battery bar and shade by hand: 1 of 4, 2 of 5, 3 of 10 in turn.

Talk this one through together — pupils take turns at the board and the whole class says the total parts aloud and names each fraction before anyone touches the slider. No copybook work here; that is the next step, so keep pencils down and eyes on the board.

Work the three ratios in the named order (1:1, 1:4, 3:2). For each, ask 'how many parts altogether?' before anyone touches the slider — the total is the denominator every time. The slider always fills to the first-named part, so on 3:2 it fills to the LARGER part; hold out for the class noticing the first part (3/5) is 60%, not a half. Once the slider is set, ask what the readout for the empty part must be so the two make 100%. If the slider is unavailable, run the same three ratios on the ten-square board bar, shading the first part by hand.

This is the practice round — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

Before each Check, ask the class to predict where the battery should sit. The order builds: 1:1 sits exactly at half because the two parts are equal, and the last one (9:1) tips well past half. Flag the switch out loud before you reveal it — ask which part they are being asked for, since it is the larger part this time, not the first-named smaller one; the on-screen label now says 'watch the switch' as a cue. Watch for the pupil who reads 2:3 as 'two thirds' and lands on 67% — send them back to the total of 5 parts. If the slider is unavailable, take a hands-up percentage for each and mark it on the ten-square board bar.