Video lessons
IB worked solutions, on video
One real exam-style question at a time, taken apart step by step on the board.
IB Physics · IB Maths AA · IB Maths AI
Latest lesson: October 15, 2026
Independent vs mutually exclusive events: Venn diagram exam question
IB Physics
How to find friction on a slope at constant speed
Friction on the slab is 12 kN and the coefficient of friction is 0.61. The whole question turns on three words in the first sentence, at constant speed, which mean every force has to cancel against another one.
IB Physics
How to find specific latent heat from a heating graph
The specific latent heat of fusion comes out at 3.4 × 10⁵ J/kg, the data booklet value for ice. The sloping minute gives the heater power (0.20 × 2100 × 20 = 8400 J in 60 s, so 140 W), the flat 8 minutes give the melting energy (140 × 480 = 6.72 × 10⁴ J), and you divide by 0.20 kg.
IB Maths AA
Independent vs mutually exclusive events: Venn diagram exam question
P(A ∩ B) = 0.21 and P(A′ | B′) = 0.7. From the Venn diagram P(A) = 0.09 + x and P(B) = 0.49 + x; independence gives x = (0.09 + x)(0.49 + x), a quadratic with discriminant zero, so x = 0.21. Independent does not mean mutually exclusive: setting x = 0 contradicts itself.
IB Maths AA
L'Hopital's rule step by step: limit of arcsin(3x)/tan(5x) as x→0
The limit is 3/5. Substituting x = 0 gives 0/0, so L'Hopital's rule applies: differentiate the top and the bottom separately (not as a quotient), 3/√(1 − 9x²) over 5sec²(5x), then let x → 0. The graph of the ratio already points at 0.6 before you differentiate anything.
First session
Find out what is costing the marks.
One to one, online, on Google Meet.