About this challenge
Library Sums is challenge 9 in the ten-part Mental Sprint collection. It uses the same core rules as the other challenges in this family, with its own settings: goal: 13; time limit: 90 seconds; number range: 41. Choose it when you want a hard round, or use the previous and next buttons to adjust the challenge.
Rules and controls
Choose the correct arithmetic answers in the illustrated world of Library Sums. Click or tap one of the four answers. Your result appears above the board when the round ends. Restart begins a new round; it does not continue the previous board. The game keeps a small record of completed rounds in this browser.
Make your next round better
Estimate the result first, then work out the exact answer. For multiplication, split a number into easier parts. For subtraction, check your answer by adding back. If the current challenge feels too demanding, go back one level and focus on the basic pattern before increasing the pace or board size.
Playing on a phone
The board adapts to the width of your screen. Use the displayed buttons or direct touch controls. For word and number inputs, tap the text field to bring up the keyboard. Put your phone in portrait orientation for the clearest view of the controls. Timing games may feel different across devices because screens and input hardware respond at different speeds.
Part of a collection, with a clear goal
This is one of ten variations of Mental Sprint, not a separate game engine. PLAYDAY contains 30 game types and 300 playable challenges in total. Each challenge has an individual page so you can return to the rules, save a favourite and choose a suitable level.
