Reasoning · Grade 2-1 Calculating to Meet Conditions
Problem
Tens weigh ten times as much, so big cards on top: 63 + 52 = 115.
Tens count for more than ones, so the biggest cards do the most good standing in the tens place — a Grade 2 place-value rule.
2.NBT.A.1Look For A PatternTo make the sum as large as possible, the biggest cards must stand in the tens places.
A card in the tens place is counted ten times over, while the same card in the ones place is counted only once.
The sum is what every card's place amount adds up to, so giving the heaviest weight to the biggest card raises the total the most.
Flip it — small cards in the tens — and 25 + 36 = 61.
Putting the small cards where they count the most (the tens) keeps the total as low as possible.
2.NBT.B.5Look For A PatternBiggest minus smallest gives 65 − 23 = 42.
To take away as little as possible from as much as possible, make the front number big and the back number small.
2.NBT.B.5Guess And CheckSqueezing the numbers together, 35 − 26 = 9 is the smallest.
When the bigger number and the smaller number are nearly equal, what's left over after subtracting is tiny — so 'close numbers' make the smallest difference.
2.NBT.B.5Make A Systematic ListPut your biggest cards in the tens place to grow a sum, the smallest cards in the tens place to shrink it — that's just Grade 2 place value at work!