Class 7 common misconceptions

Can the same digit have different values? — Tempting mistake: “The two 7s in 707,000 are worth the same.”

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

Must every operation be done left to right? — Tempting mistake: “8 + 2 × 3 = 30”

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

Which decimal is larger? — Tempting mistake: “0.35 is greater than 0.4 because 35 is greater than 4.”

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

Do like terms multiply when you add them? — Tempting mistake: “3x + 2x = 5x²”

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

Are alternate angles always equal? — Tempting mistake: “Alternate angles are equal even when a transversal crosses two nonparallel lines.”

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

Can an even total prove both addends are even? — Tempting mistake: “If a sum is even, both numbers were even.”

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

Can any three side lengths make a triangle? — Tempting mistake: “Sides 2, 3 and 6 make a triangle.”

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

Must multiplication make a fraction larger? — Tempting mistake: “½ × ⅔ must be bigger than ⅔.”

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

Does the same shape guarantee congruence? — Tempting mistake: “A 3–4–5 triangle and a 6–8–10 triangle are congruent.”

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

What does subtracting a negative do? — Tempting mistake: “3 − (−2) = 1”

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

When do you need a common factor? — Tempting mistake: “The greatest equal packet size for 12 blue beads and 18 red beads is 36.”

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

Does a trailing zero make a decimal bigger? — Tempting mistake: “0.50 is bigger than 0.5.”

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

Which group has the higher average? — Tempting mistake: “The group with the larger total always has the larger mean.”

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

Is every line through the midpoint a perpendicular bisector? — Tempting mistake: “Passing through the midpoint is enough.”

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

What happens when you move a term across an equals sign? — Tempting mistake: “From x + 3 = 10, move +3 to the right as +3 and get x = 13.”

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

Does one matching result establish a scientific rule? — Tempting mistake: “If a wide bowl of water dries before a narrow cup once, the bowl shape must be the cause.”

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

Does one unchanged litmus strip prove neutrality? — Tempting mistake: “If blue litmus stays blue, the liquid must be neutral.”

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

Does current get used up by a bulb? — Tempting mistake: “Less current leaves the bulb than enters it in a steady series circuit.”

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

Is a shiny substance always a metal? — Tempting mistake: “Shiny iodine must be a metal.”

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

Does melting make a new substance? — Tempting mistake: “Melted ice has turned into a new substance.”

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

Does the start of puberty mean growth is complete? — Tempting mistake: “The first visible sign of puberty means someone has finished growing.”

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

Does heat only travel upward? — Tempting mistake: “Heat from a heater reaches only places above it.”

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

Do stops count when you calculate average speed? — Tempting mistake: “A trip's average speed counts only the time spent moving.”

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

Is the stomach where digestion finishes? — Tempting mistake: “All digestion is finished in the stomach.”

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

Do plants get their food from the soil? — Tempting mistake: “Roots absorb the plant’s food from the soil.”

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

Is a shadow a reflection? — Tempting mistake: “A shadow is a dark image reflected by the object.”

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

Is every new moon a solar eclipse? — Tempting mistake: “The Moon is between Earth and Sun at new moon, so an eclipse must happen each month.”

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