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    Question

    The speed of a bike increases by 7 km/hr after every 1

    hour. If the distance travelled by the bike in 1st hour is 10 km, the find the total distance travelled by the bike in 14 hours.
    A 777 km Correct Answer Incorrect Answer
    B 666 km Correct Answer Incorrect Answer
    C 707 km Correct Answer Incorrect Answer
    D 797 km Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Since, the speed of the bike increases by 7 km/hr after every 1 hour, therefore the bike will travel 7 km extra after every 1 hour. Therefore, distance travelled by the bike in 1st hour = 10 km Distance travelled by the bike in 2nd hour = 10 + 7 = 17 km Distance travelled by the bike in 3rd hour = 17 + 7 = 24 km This form an AP i.e. 10, 17, 24………distance travelled in 14th hour Therefore, total distance travelled by the bike in 14 hours = sum of the AP Distance travelled in 14 hours = (n/2){2a + (n – 1)d} Where n = number of terms = 14, a = 1st term = 10 and d = common difference = 7 Therefore, distance travelled in 14 hours = (14/2){2 × 10 + (14 – 1) × 7} = (14/2)(20 + 91) = 777 km

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