Class 10 common misconceptions

Can an endless decimal be rational? — Tempting mistake: “Every decimal that goes on forever is irrational.”

1 worked visual example · 7 “If your child says…” checks

Are the zeros the coefficients? — Tempting mistake: “The zeros of x² − 5x + 6 are −5 and 6.”

1 worked visual example · 6 “If your child says…” checks

Does every pair of lines have one solution? — Tempting mistake: “Two linear equations always give one solution.”

1 worked visual example · 6 “If your child says…” checks

Can you divide away a possible solution? — Tempting mistake: “Divide x² = 3x by x and keep only x = 3.”

1 worked visual example · 6 “If your child says…” checks

Is the first term one step from itself? — Tempting mistake: “The nth term is a + nd.”

1 worked visual example · 7 “If your child says…” checks

Does similarity mean equal areas? — Tempting mistake: “Similar triangles have the same area.”

1 worked visual example · 7 “If your child says…” checks

Can opposite coordinate signs cancel the distance? — Tempting mistake: “The distance from (−3, 0) to (3, 0) is zero.”

1 worked visual example · 7 “If your child says…” checks

Can you label a side opposite without choosing an angle? — Tempting mistake: “A leg stays the opposite side when I switch the reference angle.”

1 worked visual example · 7 “If your child says…” checks

Which height does an elevation angle measure? — Tempting mistake: “The height calculated from eye level is the whole tower height.”

1 worked visual example · 5 “If your child says…” checks

Does a line through one point on a circle have to be a tangent? — Tempting mistake: “Any line drawn through a marked point on the circle is a tangent.”

1 worked visual example · 5 “If your child says…” checks

Does half the radius give half the area? — Tempting mistake: “A circle of radius 3 has half the area of one of radius 6.”

1 worked visual example · 5 “If your child says…” checks

Do joined faces still count as outer surface? — Tempting mistake: “Add both full surface areas when two cubes are joined face to face.”

1 worked visual example · 5 “If your child says…” checks

Can you ignore frequencies in the mean? — Tempting mistake: “If scores are 1 and 5, the mean is 3.”

1 worked visual example · 5 “If your child says…” checks

Does a losing streak change the next fair toss? — Tempting mistake: “After three tails, heads is more likely on the next toss.”

1 worked visual example · 4 “If your child says…” checks

Can balancing change a chemical formula? — Tempting mistake: “Write NH₃ as NH₆ to account for all six hydrogen atoms.”

1 worked visual example · 8 “If your child says…” checks

Does one pH step mean one equal unit of acidity? — Tempting mistake: “A solution at pH 3 has twice the hydrogen ion concentration of pH 6.”

1 worked visual example · 8 “If your child says…” checks

Do all metals react with water in the same way? — Tempting mistake: “Copper reacts with cold water like sodium because both are metals.”

1 worked visual example · 8 “If your child says…” checks

Can a double bond count as just one bond toward carbon’s valency? — Tempting mistake: “Each carbon in ethene makes only three bonds.”

1 worked visual example · 8 “If your child says…” checks

Does photosynthesis release oxygen taken from carbon dioxide? — Tempting mistake: “The oxygen gas comes from carbon dioxide because CO₂ contains oxygen.”

1 worked visual example · 8 “If your child says…” checks

Is a reflex a deliberate decision? — Tempting mistake: “You think about moving your hand before a withdrawal reflex.”

1 worked visual example · 8 “If your child says…” checks

Does regrowing a body part count as reproduction? — Tempting mistake: “A lizard reproduces when it regrows a lost tail.”

1 worked visual example · 8 “If your child says…” checks

Does dominant mean more common? — Tempting mistake: “A dominant allele must be found in most people.”

1 worked visual example · 8 “If your child says…” checks

Does a convex lens always form a real image? — Tempting mistake: “A converging lens always projects an image onto a screen.”

1 worked visual example · 8 “If your child says…” checks

Which lens corrects near-sightedness? — Tempting mistake: “Near-sightedness needs a converging lens to make distant objects clear.”

1 worked visual example · 8 “If your child says…” checks

Does a larger series resistor use up more current? — Tempting mistake: “Less current flows just after a 4 Ω resistor than just after a 2 Ω resistor in the same series loop.”

1 worked visual example · 8 “If your child says…” checks

Does reversing current reverse the magnetic field? — Tempting mistake: “The compass deflects the same way after reversing the current.”

1 worked visual example · 8 “If your child says…” checks

Does energy increase higher up a food chain? — Tempting mistake: “Top predators receive the most energy because they eat other animals.”

1 worked visual example · 8 “If your child says…” checks