Direct and inverse proportion

Watch: Watch whether the learner scales the 500-sheet count when the height grows from 5 cm to 7.5 cm. An entry of 500 shows the known count was copied; 250 shows only the extra half-stack was counted.

Misread: The noun to count is sheets, and the action is to find the total in the taller stack. A response of 250 gives only the added sheets, while 7.5 or a centimetre answer reports the height instead of the sheet count.

Curriculum: This is direct-proportion reasoning with constant sheet thickness: a known measure–count pair is scaled to a new measure. The scored skill is entering the exact target count using a scale factor or unit rate.