Uvero — STEM Learning

Percentage Increase and Decrease

A percentage change is calculated from the original amount. Find the change, then add or subtract it from the original. A careful solution names the quantities, keeps place value or units visible, and explains why each operation fits.

Worked reasoning

25% of 80 is 20.
Add $80+20=100$ .

Increase 80 by 25%.

Which statement best captures the central mathematical idea in Percentage Increase and Decrease?

Find the change, then add or subtract it from the original.

A familiar-looking calculation may be used without checking place value, units, conditions or what the answer represents.

A memorised formula is valid even when its conditions are not met.

The diagram or notation replaces the need to justify each mathematical step.

When starting a problem about Percentage Increase and Decrease, which move is most reliable?

Represent the given information clearly and identify the operation or relationship required for percentage increase and decrease.

Round every value before identifying the mathematical structure.

Choose the longest available formula and substitute immediately.

Assume the desired conclusion and work backwards without checking equivalence.

Which statement is a misconception that must be rejected when working with Percentage Increase and Decrease?

A familiar-looking calculation may be used without checking place value, units, conditions or what the answer represents.

Find the change, then add or subtract it from the original.

Represent the given information clearly and identify the operation or relationship required for percentage increase and decrease.

Estimate first, then reverse the operation or use a second representation to check that the answer is reasonable.