SEP23 – Problems on Numbers

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    Today, We are going to take a test on Problems based on Problems on Numbers

    Before you take the test read these posts to be comfortable.

    Shortcuts and Tips for Problems on Numbers

    Important Formulae

    In this section, questions involving a set of numbers are put in the form of a puzzle. You have to analyse the given conditions, assume the unknown the numbers and form equations accordingly, which on solving yield the unknown numbers.

    AVERAGE -> IMPORTANT FACTS AND FORMULAE

    I. Average = [Sum of observations / Number of observations]

    II. Suppose a man covers a certain distance at x kmph and an equal distance at y kmph. Then, the average speed during the whole journey is [2xy / x + y] kmph.

    Numbers -> IMPORTANT FACTS AND FORMULAE

    1. Natural Numbers :

    Counting numbers 1, 2, 3, 4, 5, .. are called natural numbers.

    Counting numbers 1, 2, 3, 4, 5, .. are called natural numbers.
    II. Whole Numbers :
    All counting numbers together with zero form the set of whole numbers. Thus,
    I. 0 is the only whole number which is not a natural number.

    II. Every natural number is a whole number.
    III.Some Important Formulae :
    I. ( 1 + 2 + 3 + …..+ n) = n (n + 1 ) / 2
    II. (1 2 + 22 + 32 + ….. + n2) = n ( n + 1 ) (2n + 1) / 6
    III. (1 3 + 23 + 33 + ….. + n3) = n2 (n + 1)2 / 4

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