How MathFun makes every question.

How does MathFun make its questions?

Questions are not written one at a time. MathFun’s own code generates them from written rules for each skill: which numbers may appear, how many digits they have, whether a problem must need regrouping, how many decimal places it uses, and which denominators are allowed.

Pressing New worksheet or New problems generates a fresh set in your browser without contacting a server. The sample questions printed on each page are fixed for that page, so the page reads the same every time you return.

Where do the answer keys come from?

The same code that builds a problem works out its answer with exact arithmetic, so the answer key always matches the questions on the page.

• Fraction arithmetic answers are in lowest terms, and answers greater than 1 are mixed numbers, such as 3/4 + 2/5 = 1 3/20.
• Division with remainders is written with R, such as 29 ÷ 4 = 7 R 1.
• Decimals drop zeros that change nothing, so 3.60 is written 3.6. Online checking accepts either form.

How does a grade page match a grade?

Grade pages follow the Common Core State Standards for Mathematics used in most US states. Each grade and operation has its own number ranges rather than one rule for every grade, and each page lists the standards its questions practice. Grade names can differ outside the US.

• Grade 1 addition: Add two numbers from 1 to 10, with sums up to 20. (1.OA.C.6)
• Grade 1 subtraction: Subtract within 20, with answers that are never below zero. (1.OA.C.6)
• Grade 2 addition: Add two-digit numbers within 100, plus some three-digit sums within 1,000. (2.NBT.B.5, 2.NBT.B.7)
• Grade 2 subtraction: Subtract within 100, plus some three-digit problems within 1,000. (2.NBT.B.5, 2.NBT.B.7)
• Grade 3 addition: Add two- and three-digit numbers with sums up to 1,000. (3.NBT.A.2)
• Grade 3 subtraction: Subtract within 1,000, with answers that are never below zero. (3.NBT.A.2)
• Grade 3 multiplication: Practice multiplication facts with factors from 1 to 10. (3.OA.C.7)
• Grade 3 division: Practice division facts within 100 with divisors from 2 to 10. (3.OA.C.7)
• Grade 4 addition: Add four- to six-digit whole numbers. (4.NBT.B.4)
• Grade 4 subtraction: Subtract multi-digit whole numbers up to six digits. (4.NBT.B.4)
• Grade 4 multiplication: Multiply up to four-digit numbers by one digit, and two-digit numbers by two-digit numbers. (4.NBT.B.5)
• Grade 4 division: Divide up to four-digit numbers by one-digit divisors, with remainders in some problems. (4.NBT.B.6)
• Grade 5 addition: Add decimals to hundredths and multi-digit whole numbers. (5.NBT.B.7, 4.NBT.B.4)
• Grade 5 subtraction: Subtract decimals to hundredths and multi-digit whole numbers. (5.NBT.B.7, 4.NBT.B.4)
• Grade 5 multiplication: Multiply three-digit numbers by two-digit numbers. (5.NBT.B.5)
• Grade 5 division: Divide three- and four-digit numbers by two-digit divisors, with remainders in some problems. (5.NBT.B.6)

What do the difficulty levels mean?

A level changes the kind of problem, not the grade. On fraction addition, levels 1 to 5 move from like denominators to unlike denominators and mixed numbers; levels 6 to 10 are challenge levels with larger denominators. Each skill page lists what every level covers with an example.

Every skill, the grades it usually belongs to, and the standards it practices:

• Adding Fractions: Grades 4–5 (4.NF.B.3, 5.NF.A.1)
• Subtracting Fractions: Grades 4–5 (4.NF.B.3, 5.NF.A.1)
• Multiplying Fractions: Grades 4–5 (4.NF.B.4, 5.NF.B.4, 5.NF.B.6)
• Dividing Fractions: Grades 5–6 (5.NF.B.7, 6.NS.A.1)
• Addition within 10, 20 & 100: Grades 1–2 (1.OA.C.6, 2.OA.B.2, 2.NBT.B.5)
• Subtraction within 10, 20 & 100: Grades 1–2 (1.OA.C.6, 2.OA.B.2, 2.NBT.B.5)
• Addition without Regrouping: Grades 2–4 (2.NBT.B.5, 2.NBT.B.7, 4.NBT.B.4)
• Addition with Regrouping (Carrying): Grades 2–4 (2.NBT.B.5, 2.NBT.B.7, 4.NBT.B.4)
• Subtraction without Regrouping: Grades 2–4 (2.NBT.B.5, 2.NBT.B.7, 4.NBT.B.4)
• Subtraction with Regrouping (Borrowing): Grades 2–4 (2.NBT.B.5, 2.NBT.B.7, 4.NBT.B.4)
• Times Tables Quiz (1–12): Grades 3–4 (3.OA.C.7)
• Division Facts: Grades 3–4 (3.OA.C.7)
• Division with Remainders: Grades 4–5 (4.NBT.B.6, 5.NBT.B.6)
• Missing Number: Grades 1–2 (1.OA.D.8, 2.OA.B.2)
• Adding Decimals: Grades 5–6 (5.NBT.B.7, 6.NS.B.3)
• Subtracting Decimals: Grades 5–6 (5.NBT.B.7, 6.NS.B.3)
• Multiplying Decimals: Grades 5–6 (5.NBT.B.7, 6.NS.B.3)
• Dividing Decimals: Grades 5–6 (5.NBT.B.7, 6.NS.B.3)
• Decimal Place Value: Grades 4–5 (4.NF.C.6, 5.NBT.A.3)
• Comparing Decimals: Grades 4–5 (4.NF.C.7, 5.NBT.A.3)
• Rounding Decimals: Grade 5 (5.NBT.A.4)
• Decimals × and ÷ by 10, 100, 1000: Grade 5 (5.NBT.A.2)
• Fraction Models: Grade 3 (3.NF.A.1)
• Equivalent Fractions: Grades 3–4 (3.NF.A.3, 4.NF.A.1)
• Simplifying Fractions: Grade 4 (4.NF.A.1)
• Comparing Fractions: Grades 3–4 (3.NF.A.3, 4.NF.A.2)
• Mixed Numbers to Improper Fractions: Grade 4 (4.NF.B.3)
• Improper Fractions to Mixed Numbers: Grade 4 (4.NF.B.3)
• Fractions on a Number Line: Grade 3 (3.NF.A.2)

How are the worked examples checked?

Every worked example on a skill page, quiz page, or level list is recomputed by an automated test that does its own arithmetic, separately from the code that makes the questions. Examples that depend on a picture, such as a shaded bar or a number line, are checked by hand.

Other tests check that every grade page lists only standards that match its operation, that questions stay inside each page’s number ranges, and that sample questions never repeat or include giveaways such as 5 − 5 or ÷ 1.

Who makes MathFun?

MathFun is built by Howard, a parent who made it for his own two kids. Questions or corrections are welcome at team@mathfun.me.

What is MathFun not?

MathFun is practice, not a curriculum or a standardized test. It does not teach every standard for a grade, and the math check-in suggests what to practice next rather than diagnosing a child. A teacher or a school’s own curriculum decides what a child needs to learn.