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Example 7: How many two-digit numbers are divisible by 3? |
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Answer» So, the A.P. will be12,15, 18,21, ………….99 We need to find n Last term of this series is 99 So, an = 99 & a =12d =15–12= 3 Now, an = a + (n – 1) d Putting values 99 =12+ (n – 1) (3) 99 =12+ 3n – 3 99 = 9 + 3n 3n = 99 – 9 3n =90n =90/3 = 30 Therefore , there are30 twodigit numbers divisible by 3 |
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