Both plans cost the same at 50 + 0.20m = 30 + 0.30m, giving 0.10m = 20, so m = 200 minutes. Plan B is cheaper for under 200 minutes; Plan A is cheaper for over 200 minutes.
NCERT Solution for Class 9 Ganita Manjari Part 2 chapter 13 question answer
NCERT Solution for Ganita Manjari Part 2 chapter 13 Two Variables, One Line solutions
Equating both monthly costs gives 50 + 0.20m = 30 + 0.30m, where m is the call duration in minutes. Simplifying yields 0.10m = 20, which gives m = 200 minutes for equal cost. For call durations under 200 minutes, Plan B is cheaper due to its lower fixed base fee. For call durations exceeding 200 minutes, Plan A is cheaper due to its lower per-minute call rate.
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