Question 4(a)
[Maximum number: 2]
The first, second and third terms of a progression are 20, k and k-5 respectively.
Given that the progression is arithmetic, find the 30th term.
CAIE A-Level Mathematics 1.6.3 Progression Formulae
Practise using nth-term and sum formulae for arithmetic and geometric progressions and forming linked equations when terms or partial sums create a second progression.
How this is tested
- identify a, d or r from given terms before applying the correct nth-term formula
- substitute n, a and d or r into the finite-sum formula and simplify accurately
- translate arithmetic or geometric conditions into equations such as 2b = a + c or b² = ac