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A sum of Rs 700 is to be used to give 7 cash prizes to students. If each prize is Rs 20 less than its preceding prize, find the value of the highest (1st) prize in rupees.

Class 10Arithmetic ProgressionsAlgebra — Sequences
  • A160
  • B145
  • C320
  • D175

Step-by-Step Solution

7 prizes in AP, , sum = 700. S₇ = → → → → rupees.
Answer: A) 160

Key idea: Common AP word problems

**Salaries**: 'Person earns ₹X in year 1 with annual increase of ₹Y. Find salary in year n / total over n years.' → AP with a = X, d = Y.

**Stadium seating**: 'Front row has 30 seats; each row 4 more. 25 rows. Total seats?' → AP with a = 30, d = 4. S₂₅ = ?

**Loans/installments**: equal monthly payments form an AP.

**Number patterns**: 'Multiples of 5 between 100 and 500: how many? Sum?' → AP with a = 100, d = 5, last = 500.

Always identify a, d, and what's asked (term aₙ or sum Sₙ). Check whether n is the COUNT or the POSITION.

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