Ordinary level 2026 north west regional mock mathematics guide

I have extracted the text from the new image, which contains mark schemes and solutions for mathematical problems involving commerce and sequences.

3(i) Commerce/Financial Math

• a) $\frac{5}{100} (25000 + 50000) = 3750f$

• b) Customer pays $75000 – 3750 = 71250f$

• c) $800 \times 71250 = 57,000,000f$

• d) $3750 \times 800 = 3,000,000f$

3(ii) Sales Calculations

• a) Only modems: $25000 \times 50 = 1,250,000f$

• b) Only phones: $50000 \times 250 = 12,500,000$

• c) All sales: $1,250,000 + 12,500,000 = 13,750,000f$

4(i) Arithmetic Progressions (AP)

• a) $U_n = 3n – 1$

  • $U_1 = 2$

  • $U_2 = 5$

  • $U_3 = 8$

  • $U_4 = 11$

  • Sequence: $2, 5, 8, 11, \dots$

• b) $U_n – U_{20} = 45$

  • $(3n – 1) – (3 \times 20 – 1) = 45$

  • $3n – 1 – 59 = 45$

  • $3n – 60 = 45$

  • $3n = 105$

  • $\therefore n = 35$

• c) Common difference $d = 8 – 5 = 5 – 2 = 3$

  • First term $a = 2$, and $n = 20$

  • Using $S_n = \frac{n}{2}[2a + (n – 1)d]$:

  • $S_{20} = \frac{20}{2}[2(2) + 3(19)]$

  • $S_{20} = 10[4 + 57]$

  • $S_{20} = 610$

Would you like me to explain the formula for the sum of an arithmetic progression used in question 4(c)?