A cooling process records a temperature of 40 °C on the first day

MATHEMATICS · Single correct · A Level · Mathematics · Sequences and series · Sequences and series

Problem

A cooling process records a temperature of 40 °C on the first day. The temperature drops by 1.8 °C each day, forming an arithmetic progression. On which day will the temperature first fall below 20 °C? (a) 12th (b) 14th (c) 13th (d) 11th

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