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Standard deviation is the square root of the variance: for 2, 4, 4, 4, 5, 5, 7, 9 the squared deviations total 32, so the population SD is exactly 2 and the sample SD is about 2.138. This guide explains n versus n − 1 and works a second dataset in full.
Asad · Oct 17, 2026 Read article →A weighted average multiplies each value by its weight, adds the products, and divides by the total weight: 0.4 × 80 + 0.6 × 70 = 74. This guide also works grades of 90, 75 and 85 at weights 3, 2 and 1 through to 505 ÷ 6 ≈ 84.17, and explains GPA-style weighting.
Asad · Oct 17, 2026 Read article →An average is the sum divided by the count: 72 + 85 + 90 + 68 + 95 = 410, and 410 ÷ 5 = 82. This guide covers the median, mode and range alongside the mean, and shows exactly how one outlier score of 20 pulls the mean down to about 71.67.
Asad · Oct 17, 2026 Read article →Add and subtract fractions over a common denominator, multiply straight across, and divide by the reciprocal: 3/4 + 2/3 = 17/12 = 1 5/12, and simplifying 24/36 by its GCD of 12 gives 2/3. Mixed numbers, improper fractions and decimals covered in full.
Asad · Oct 17, 2026 Read article →Adding sales tax is price times (1 + rate): $200 at an example 8 percent becomes $216. Extracting it is the reverse division: $216 divided by 1.08 is $200 net with $16 of tax inside. This guide covers both directions, why subtraction fails, and why US rates vary by state and city — all rates here are examples only.
Asad · Oct 16, 2026 Read article →A tip is bill times percentage divided by 100: 18 percent on $86 is $15.48, making a $101.48 total and $25.37 each split four ways. This guide covers pre-tax versus post-tax tipping, rounding described as custom rather than rule, and proportional splits for groups whose orders differ.
Asad · Oct 16, 2026 Read article →Percentage change is (new − original) ÷ |original| × 100 — so 80 to 100 is +25%, and +50% followed by −50% lands at 75, not 100. This guide covers change between two values only, including percentage points versus percent.
Asad · Oct 16, 2026 Read article →A discount is price times percentage divided by 100 for the saving, then the saving subtracted for the final price: 30 percent off $250 saves $75 and leaves $175. This guide covers stacked offers — 20 percent then 10 percent is 28 percent in total, not 30 — percentage points, and working backwards from a sale price.
Asad · Oct 16, 2026 Read article →Simplifying a ratio means dividing both terms by their greatest common divisor: 24:36 with a GCD of 12 becomes 2:3. This guide covers scaling a ratio to any total, reading a ratio as percentages through the sum of its parts, and how ratios differ from fractions — plus 16:9 screens worked from real pixel counts.
Asad · Oct 16, 2026 Read article →One foot-candle is 10.7639 lux and one phot is 10,000 lux, so a typical 500 lux office is about 46.5 foot-candles. This guide gives the factors, three worked examples, and typical anchors from living rooms to overcast daylight.
Asad · Oct 16, 2026 Read article →One litre per second is 60 L/min, 3.6 m³/h, about 15.85 US gallons per minute and about 2.119 CFM. This guide gives the exact factors, three fully worked pump examples, and the checks that catch a flow conversion before it costs money.
Asad · Oct 16, 2026 Read article →A US cup is 236.588 mL and a metric cup is 250 mL — a 13.41 mL gap in every cup. This guide gives the exact size of all six measures, works a full recipe conversion, and explains why volume never converts honestly to weight.
Asad · Oct 16, 2026 Read article →This conversation is closed — thanks for chatting with us.
