River Expedition

Two baskets of berries have to become one snack before dark. You choose which basket to pour, then whether to join them or eat from only one.

Grades K, 1 · add-within-10

A canoe had enough paddles at dawn. Some floated off. You choose which canoe to search, then whether to find the missing part or subtract by grabbing extras from another boat.

Grades K, 1 · subtract-within-10

A crossing needs sums within 20. You choose a ford, then whether to make a ten first or add the ones in a tangle.

Grades 1, 2 · make-ten-20

Two supply counts within 100 have ones that do not overflow. You choose a canoe, then whether to add by places or by dumping both lists together.

Grades 2 · add-two-digit

Ones overflow into a ten on a muddy trail count. You choose a wagon, then whether to trade ten ones or pretend the ones digit can be 12.

Grades 2, 3 · regroup-add

Two trail lengths need a difference. You choose which blazes to compare, then whether to subtract by places or by guessing the gap from the map's picture.

Grades 2, 3 · subtract-two-digit

The big cache is counted in hundreds. You choose a cache, then whether to add by places through hundreds or estimate and call it exact.

Grades 3, 4 · add-sub-1000

A fork in the trail needs a reasonable estimate before an exact check. You choose a fork, then whether to round first or march on an exact count you have not finished.

Grades 3, 4 · estimate