Reverse reasoning

Find the starting number by undoing the operations.

How it works

Start from the result and apply the inverse operations backwards.

• 30 progressive levels, from basic to advanced
• Levels 1 to 3 free, no card

More exercises in Maths and numbers

• Mental arithmetic
• Hidden operation
• Mystery number
• Number pyramid
• Number sequences
• Estimation
• Visual fractions
• Percentages
• Ratio and proportion
• Divisibility
• Magic square
• Combinatorics
• Probability
• Olympiad problems