Number Concepts and Operations
The first score-report subject area: the four operations, signed numbers, factors, fractions, decimals, rational numbers and estimation with no calculator.
7 topics · 30 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
The Four Operations and Order of Operations
- How it worksHow does the order of operations unwrap an expression from the innermost parentheses outward?
- Worked exampleFind the value of 6 + 3 × (8 - 2)² ÷ 4, one operation at a time.
- Common mistakeWhy doesn't multiplication always come before division in the order of operations?
- Going furtherWhat happens to 12 - 4 - 3 when you work it right to left instead of left to right?
Negative Numbers and Signed Arithmetic
- How it worksHow do two minus signs cancel in a product, drawn as a flip across zero and then a flip back?
- Worked exampleFind the value of -7 - (-12) + (-4) by walking each step along a number line.
- Worked exampleFind the values of (-2)⁵ and (-2)⁴, and show why only one of them comes out negative.
- Common mistakeWhy isn't -3² equal to 9 when squaring is supposed to erase the minus sign?
- Going furtherWhat happens to -2x < 6 when you divide both sides by that negative 2?
Factors, Multiples, Primes, GCF and LCM
- How it worksHow does a factor tree break any whole number down into one unique pile of primes?
- Worked exampleFind the greatest common factor and the least common multiple of 24 and 36.
- Worked exampleFind how many positive factors 60 has without listing every single one of them.
- Common mistakeWhy isn't 1 counted as a prime number when nothing divides it except itself and one?
Operations with Fractions
- How it worksHow does multiplying a fraction by a disguised form of 1 change its look without changing its size?
- Worked exampleFind 2/3 + 3/4 - 5/6 as one fraction in lowest terms.
- Worked exampleWalk me through dividing 3/8 by 5/6, and show why flipping the second fraction works.
- Common mistakeWhy doesn't multiplying by 3/4 make a number bigger the way multiplying usually does?
- Worked exampleFind which is larger, 7/9 or 5/7, without turning either one into a decimal.
Decimals, Place Value and Rounding
- How it worksHow does place value split 0.407 into four tenths, zero hundredths and seven thousandths?
- Worked exampleFind the product 0.04 × 0.25 and show where the decimal point has to land.
- Worked exampleWalk me through rounding 3.6482 to the nearest tenth and then to the nearest hundredth.
Rational Numbers and the Number Line
- How it worksHow does long division turn any fraction into a decimal that either stops or repeats forever?
- Worked exampleFind the order of -2/3, -0.7, -3/5 and -0.66 from least to greatest along a number line.
- Common mistakeWhy isn't every decimal you can imagine writing down a rational number?
- Going furtherWhat happens to the repeating decimal 0.272727 when you convert it back into a fraction?
Estimation and Approximation
- How it worksHow does rounding one factor up and the other down keep an estimate close to the true product?
- Worked exampleFind a fast estimate for 6842 ÷ 68 and choose between 10, 100 and 1000.
- Worked exampleWalk me through estimating 48 percent of 610 closely enough to pick from five spread-out choices.
- Common mistakeWhy doesn't rounding both numbers up give a usable estimate when you are subtracting?
- Going furtherWhat changes about estimating when the five choices are 0.28, 0.30, 0.32, 0.34 and 0.36?
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