Number Play
Enable JavaScript for interactive models and guided question help.
Build a number from its neighbours
Start with 3,4,5,6: each number is one more than the last. Change the first number or how many terms you use. Can the sum reach 15?
Flip a sign. What stays the same?
Read the selected sum. Predict whether its odd/even kind will change, then flip one sign. Open the comparison only when you want all eight results.
Even or odd? Find the pairs
Odd numbers leave one unpaired unit; even numbers form complete pairs. Choose an expression, predict Even/Odd or Always/Sometimes/Never, then open Understand it.
Two leftovers can make a full group
Try 6 and 10. In each colour, look for the dots outside full fours. Predict Yes or No, then combine. Next compare 8 and 6.
A claim needs more than examples
“Always” means every allowed case works; “Never” means none works. Choose “Sometimes” when you can find both a success and a failure. Test the selected statement.
Make groups. Keep the leftovers.
The outlined groups hold five dots each. Count the dots left in the unfinished group for 23. Predict what changes when you add five.
Why do the last digits decide?
With divisor 4, split 427 into 400 and 27. Which part already divides exactly? Change 427 to 727 while keeping the same final two digits.
Trade place values for leftovers
Start with 427. The cards label its hundreds, tens and units. Predict how much is left after you remove complete multiples of 9 from each part.
A quick test for eleven
Try 462. Its cards show + at units, − at tens, + at hundreds. Before using the shortcut, compare 100 with 99 and 10 with 11.
Be the divisibility detective
Choose a number. Start with the last-digit tests for 2,5,10. Predict each answer, check the row, then open “Why this test?” for any result you need to understand.
Two tests: which factors are guaranteed?
Keep tests 4 and 6 with target 24. Find a number that passes both tests but fails the target. Tap 12 to inspect its three remainders.
Follow a digital-root cycle
For 489710, predict the digit total before pressing “Add its digits”. If the result still has two digits, repeat. Then compare a sequence.
Digits in disguise
Each letter hides one digit. The same letter must repeat its digit; different letters must differ. A number cannot start with 0. Start with the rightmost column, or open the first hint.
A multiple can belong to several sets
The diagrams show sets of MULTIPLES, not three individual numbers. Choose one, then test 4,8,32 to see where each number belongs.
Figure it out, with a little help
Choose the page printed in your textbook, then a question. Try its first move yourself. A hint offers one next move; Understand it explains the reasoning; the exam answer is separate.
Navakankari: make a line of three
Take turns placing one pawn on an empty point. Look for THREE connected points on one drawn straight line. Completing a line lets you remove an opponent’s unprotected pawn.
Explain why, not just what
Choose an idea you want to explain. Before opening its answer, give a small example and say what the example helps you notice.
Back to Mathematics