A) 266 km
B) 273 km
C) 280 km
D) 287 km
Correct Answer: B
Solution :
Sol. [b] Speed in first hour is 30 km/h. Now for 1 h, the distance covered = speed of that hour. \[\therefore \]The distance will form an AP with a = 30, d = 3 and n = 7 \[\therefore \,\,\,\,{{S}_{n}}\,\,=\,\frac{n}{2}\,[2a+(n-1)d]\] \[{{S}_{7}}\,=\,\frac{7}{2}\,[2\times 30+(7-1)(3)]\] \[{{S}_{7}}\,=\,\frac{7}{2}\,[60+18]\] \[{{S}_{7}}\,=\,\frac{7}{2}\,\times \,78\Rightarrow {{S}_{7}}\,=273\,km\] \[\therefore \]Total distance covered in 7 h is 273 km.
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