Question

Nandani and Krithika measure the temperature of a piece of metal before and after being set on a block of ice. The original temperature of the metal is 72.935°F. After sitting on the block of ice for 5 minutes, the temperature of the metal is 51.28°F.

Krithika calculates the temperature change as shown.
A vertical equation shows seventy-two point nine three five minus fifty-one point two eight equals sixty-seven point eight zero seven.
Nandani points out that this is not the change in temperature.

Find Krithika’s mistake.
Click or tap the correct answer from the drop-down menu.
Krithika’s mistake was that she
Choose
should have added and not subtracted
did not need to regroup
subtracted in the wrong order
needed to add a zero to align the decimal points
.
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Answer 1

Krithika’s mistake was that she needed to add a zero to align the decimal points.

With the zero: 72.935 − 51.280 = 21.655, so the temperature changed by 21.655°F.