GCD 12, LCM 72

Over 30 → ²⁵⁄₃₀ ＋ ⁹⁄₃₀ = ³⁴⁄₃₀ → ¹⁷⁄₁₅ = 1²⁄₁₅

GCD 14 → ³⁄₄

Over 24 → ²¹⁄₂₄ − ¹⁰⁄₂₄ = ¹¹⁄₂₄

Over 36 → ²¹⁄₃₆ against ²⁰⁄₃₆ → ⁷⁄₁₂ is larger

4 and 6 give 12; then 12 and 15 give → 60

LCM of 18 and 24 → 72 seconds

Over 12 → ¹⁰⁄₁₂ − ³⁄₁₂ − ⁴⁄₁₂ = ³⁄₁₂ = ¹⁄₄ m

Over 24 → ¹⁶⁄₂₄, ¹⁵⁄₂₄, ¹⁴⁄₂₄ → ⁷⁄₁₂ < ⁵⁄₈ < ²⁄₃

GCD of 48 and 72 is 24 → one piece 24 cm. 48÷24 = 2, 72÷24 = 3 → 5 pieces

No right answer. A reason is enough. Which one he picks is a hint for choosing October's costumes.

4032÷1008 = 4, 3024÷1008 = 3 → 4 : 3

LCM of 14 and 21 is 42 teeth. The 14 turns 42÷14 = 3 times, the 21 turns 42÷21 = 2 times

F: 72 x ³⁄₄ = 54 cm; G: 72 x ²⁄₃ = 48 cm

3H₂ ＋ N₂ → 2NH₃. N: 2 on the left → two NH₃. H: 6 on the right → three H₂.

1 GCD / 2 LCM / 3 fractions / 4 LCM.

What matters is whether he saw that 2 and 4 are the same tool. Gears and chemical equations look the furthest apart of the four and are the same thing inside.

³⁄₄ = 0.75, ¹⁄₅ = 0.2.

Both come from numerator ÷ denominator (3÷4, 1÷5). October's 'dividing decimals' continues from here.

0.6 = ⁶⁄₁₀ → cancel by 2 → ³⁄₅

1 ÷ 8 = 0.125

Any workable question counts. Check his answer with him.

Being able to write the question means knowing when the tool is the right one. That is the thing worth checking at the end of September.