Decimals: 4th grade math in The Grasslands and Forests of India

Singapore teaches decimals to 3 places and their four operations in Primary 4; in the US they finish in grade 5.

Tiptoe through tall grass with rhinos, tigers and dancing peacocks across India. Characters here greet you with “Namaste!” (hello in Hindi (it means “I bow to you”)), and eggs hatch into hybrids of animals like Bengal tiger, fishing cat, Indian rhinoceros and wild water buffalo.

What your child practices

Follows Decimal notation (4.NF.C) with a preview of decimal operations (5.NBT).

• Tenths, Hundredths & Thousandths

  Read and write decimals, find what each digit is worth, and place decimals on a number line.

  4.NF.C.6, 5.NBT.A.3a

• Comparing & Ordering Decimals

  Find which decimal is greater and put decimals in order, up to 3 decimal places.

  4.NF.C.7, 5.NBT.A.3b

• Fractions & Decimals

  Turn decimals into fractions, and fractions like 3/4 or 7/20 into decimals.

  4.NF.C.5, 4.NF.C.6

• Rounding Decimals

  Round decimals to the nearest whole number, 1 decimal place or 2 decimal places.

  5.NBT.A.4

• Adding & Subtracting Decimals

  Add and subtract decimals, estimate the answer, and check that it makes sense.

  5.NBT.B.7

• Multiplying & Dividing Decimals

  Multiply and divide decimals by a 1-digit number, and round the answer when asked.

  5.NBT.B.7

• Dividing with Decimal Answers

  Divide whole numbers and keep going past the point: 7 ÷ 4 = 1.75.

  5.NBT.B.7

• Decimal Word Problems

  Solve 1- and 2-step decimal stories, estimate, and check that answers make sense.

  5.NBT.B.7

Try a problem from The Grasslands and Forests of India

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.

• Place value

  The digits are right but their places are not: a 3 in the tens is worth 30, not 3. This shows up when carrying, borrowing, lining up numbers or placing a decimal point.

  Mistakes we catch: tens for tenths, miscounted decimal places, missing placeholder zero, wrong size for each mark, ignored a zero after the point, always rounds down, rounded to the wrong place, rounded in steps, lined up the last digits, took the smaller digit from the larger, point in the wrong place, misplaced point in a product, misplaced point in a quotient and did not check the size.

  Try at home: Write a number on paper with a column for thousands, hundreds, tens and ones. Take turns saying what each digit is worth, then add or subtract by trading between columns out loud ("ten ones make a ten").

• 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 from the wrong end.

  Try at home: Draw a number line and hop along it in 2s, 5s or 10s. For “posts and gaps” questions, sketch 3 posts and count the gaps before doing the big number.

• Fractions and decimals

  Treating the top and bottom of a fraction as two separate whole numbers (so 1/2 + 1/3 = 2/5), thinking a bigger bottom number means a bigger piece, or reading 0.25 as bigger than 0.3.

  Mistakes we catch: longer means larger, shorter means larger, tenths and hundredths mixed up, fraction bar as a decimal point, wrote only the top number, dropped the whole number, only used the whole number part and remainder as the decimal.

  Try at home: Use a chocolate bar or paper strips to compare fractions: is 1/3 or 1/5 bigger? Line up fraction strips to find equal ones (2/4 = 1/2).

• 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: ordered the wrong way.

  Try at home: For subtraction, read the top number first every time (“52 take away 37”). For division, say “how many 4s fit in 20?” so the order is clear.

• 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: worked out the exact answer, dropped the remainder and stopped after one step.

  Try at home: Before solving, ask them to finish the sentence “The answer will be the number of …”. After solving, check that the answer fits that sentence.

• 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: used the wrong operation.

  Try at home: Read a word problem together and draw it as a quick picture or bar before choosing + − × ÷. Ask “is the answer bigger or smaller than the numbers we started with?”

More Grade 4 worlds: Big Numbers · Factors & Patterns · Fractions · Measurement & Data · Lines, Angles & Shapes