HOW ROUNDING WORKS

1. Find the two friendly numbers the value sits between.
2. Mark the midpoint. That is the halfway house.
3. If the number is before the midpoint, stay with the lower friend.
4. If it hits the midpoint or goes past, take the higher friend. 5 rounds up.

Example: 73 lives between 70 and 80. Midpoint 75. 73 is closer to 70.

HOW PLACE VALUE WORKS

1. Every digit has a house. Ones, tens, hundreds, and so on.
2. A digit means that many groups of its house. 4 in the thousands house is 4 groups of 1,000.
3. Ten of one house make one of the next house.
4. Read the number by naming each house from left to right.

Example: 4,072 is 4 thousands, 0 hundreds, 7 tens, 2 ones.

ADD WITHOUT REGROUPING

1. Line the numbers up by house: ones under ones, tens under tens.
2. Start at the ones. Add only that column.
3. If the two digits make 9 or less, write that sum in the house. No extra ten is carried.
4. Move left one house at a time until the sum is complete.

Example: 34 + 21. Ones 4+1=5. Tens 3+2=5. Sum 55.

REGROUP · CARRY AND BORROW

1. Work one house at a time, starting at ones.
2. Add: if a column makes 10 or more, write the ones digit and send one ten to the next house.
3. Subtract: if the top digit is too small, tap that next house, cross it out, and send ten to the house that needs it.
4. Level 1 lights the next tap. Level 5 does not.

45 − 28: 5 cannot give 8. Tap 4, write 3 above it, ones become 15, then 15 − 8 = 7.

PROPERTIES AT A GLANCE

1. Operation properties say what + and × are allowed to do.
2. Equality properties say what you may do to both sides of an equation.
3. Commutative = order. Associative = grouping. Distributive = sharing across a sum.
4. Identity leaves a number itself. Inverse undoes it back to 0 or 1.

Tap a card for the meaning. Tap SWAP / GROUP / SHARE to see the move.

TELL THE TIME

1. Short stick is the hour. Long stick is the minute.
2. Tap the time that matches the clock.
3. Ten rounds. Instant yes or try again.