q-a1.ns.8 - Jill gave money to a charity over a 20-year period, from Year 1 to Year 20 inclusive. She gave £150 in Year 1, £160 in Year 2, £170 in Year 3, and so on,

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q-a1.ns.8

Anonymous

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so that the amounts of money she gave each year formed an arithmetic sequence.

a) Calculate the total amount of money she gave over the 20-year period.

Krishna (last edited 5 years ago) (Expert, Educator @Qalaxia)

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STEP 1: Identify the first term in the sequence, call this number a.

STEP 2: Calculate the common difference(d) of the sequence.

STEP 3: Identify the number of terms (n).

[EXAMPLE: In A.P 2, 4, 6,..... find the sum of the first 10 terms. So take n =10]

STEP 4: Plug the values of n, d, and a into the formula.

[FORMULA: The formula for finding the sum of first n terms of an arithmetic sequence (S_n) =(n/2)[2a + (n- 1)d]

STEP 5: Simplify further.