Maharashtra BoardEnglish MediumSTD 10MathsP-1 Arithmetic Progression3 Marks
Question
Find how many three digit natural numbers are divisible by 5.
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Answer
List of three digit number divisible by 5 are 100, 105,110,115,……….. 995 Let us find how many such number are there? From the above sequence, we know that tn = 995, a = 100 t1 = 105, t2 = 110 Thus, d = t2 – t1 = 110 – 105 = 5 Now, By using nth term of an A.P. formula tn = a + (n – 1)d we can find value of “n” Thus, on substituting all the value in formula we get, 995 = 100 + (n – 1)× 5 ⇒ 995 – 100 = (n – 1)× 5 ⇒ 895 = (n – 1) × 5 $\Rightarrow n -1=\frac{895}{5}=179$ ⇒ n = 179 + 1 = 180
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