Adding & Subtracting to 20: 1st grade math in The Scottish Highlands

Adding and subtracting within 20, fact families, adding three numbers, story problems and missing numbers.

Walk through purple heather, meet shaggy Highland cows and hear bagpipes echo across the lochs. Characters here greet you with “Halò!” (hello in Scottish Gaelic), and eggs hatch into hybrids of animals like red deer, reindeer, mountain hare and ptarmigan.

What your child practices

Follows Operations & Algebraic Thinking (1.OA).

• Adding and subtracting within 20

  Add and take away numbers up to 20 to build fences, meadows and bridges.

  1.OA.A.1, 1.OA.A.2, 1.OA.C.5, 1.OA.C.6

• Fact families

  Use one adding fact to find the take-away facts that go with it.

  1.OA.B.4, 1.OA.C.6

• Adding three numbers

  Add three numbers, making ten first when you can.

  1.OA.A.2, 1.OA.B.3

• Story problems within 20

  Solve short adding and take-away stories from the Highlands.

  1.OA.A.1

• How many more?

  Compare two groups and find how many more or how many fewer.

  1.OA.A.1

• Finding the missing number

  Find the number that makes an adding or take-away sentence true.

  1.OA.D.8

• True or false?

  Decide if both sides of the = sign are the same amount.

  1.OA.D.7

• Make ten and count on

  Add and take away in your head by making ten or counting on.

  1.OA.C.6

Try a problem from The Scottish Highlands

Every problem is a short story set in the world. These are real problems from the game. Kids get endless new ones with different numbers.

Common mistakes, and how to help

Every wrong answer in Mixmonde is planned: it points to a named mistake, and the tip after a miss explains it with that problem’s numbers. These are the mistakes this world watches for, grouped the way the grown-ups’ dashboard shows them.

• Units and measuring

  The number is fine but the unit is off: a missing conversion (cm and m), the ruler not started at zero, or area mixed up with perimeter.

  Mistakes we catch: missed a side and added a side that isn’t there.

  Try at home: Measure things at home with a ruler, starting at 0, and with hand spans or shoes. Ask which is longer and by how much.

• Choosing the operation

  The arithmetic is fine, but the wrong operation was picked: adding when the story takes away, or multiplying when it shares out.

  Mistakes we catch: added instead of taking away, added to the whole, wrong operation, added instead of comparing and used the wrong operation.

  Try at home: Act out word problems with toys: “3 birds, 2 fly away.” Ask “are we putting together or taking away?” before any numbers.

• Reading the question

  The math works, but the answer is to a different question: a number already given, a halfway step, or only part of a two-step problem.

  Mistakes we catch: gave the part that was given, gave the starting number, counted meters, not planks, gave the part taken away, left out a number, gave a number from the story, gave the bigger number, gave the smaller number and gave a number already shown.

  Try at home: Read the question aloud together and ask “what are we trying to find?” before solving. Point at the question part of the sentence.

• Order and direction

  The right idea done the wrong way round: taking the smaller digit from the bigger one, dividing backwards, swapping x and y, or flipping more and less.

  Mistakes we catch: took one part from the other.

  Try at home: Use “more” and “fewer” in everyday talk: which plate has more grapes, how many fewer? Line things up side by side to compare.

• Counting and sequences

  Losing track while counting: off by one, skipping or double-counting, or counting the wrong things (fence posts instead of gaps).

  Mistakes we catch: counted the start again.

  Try at home: Count objects by touching or moving each one into a pile. Count on from a number other than 1 (“start at 8 and count 5 more”), and count back too.

• Expressions and equations

  Order of operations, unknowns and the equals sign: reading “=” as “the answer comes next” instead of “both sides balance”.

  Mistakes we catch: thought order changes the total, thought the answer must come last, read = as "the answer is", checked only one number and thought the numbers must match.

  Try at home: Play balance games: “I have 5 on this side, how many on the other to make it even?” with toys or a seesaw drawing.

• Number facts

  The method is right, but a basic fact or one step of the arithmetic slipped. Usually a sign that facts are still being worked out each time instead of remembered.

  Mistakes we catch: forgot the leftover and used the whole number again.

  Try at home: Play “make 10” with fingers or a deck of cards (pairs that add to 10), then “make 20”. Two minutes a day beats one long session.

More Grade 1 worlds: Numbers to 100 · Adding & Subtracting to 100 · Length, Time & Graphs · Shapes & Equal Shares · Equal Groups & Money