A person is to count 4500 currency notes. Let denote the number of notes he counts in the minute. If and are in an A.P. with common difference -2 , then the time taken by him to count all notes is...

First 10 minutes = 150 10 = 1500 148 + 146 + 144 + 3000 = 296n - 2n^2 + 2n2 4500 = 1500 + n2 ( 296 + (n - 1)(-2) ) 2n^2 + 298n + 6000 = 0 n^2 - 149n + 3000 = 0 n^2 - (125 + 24)n + 125 24 = 0 (n - 24)(n - 125) = 0 n = 24 or n = 125 n eq 125 n = 24 Total time = 24 + 10 = 34 minutes...

A person is to count 4500 currency notes. Let a_{n} denote the number of notes he counts in the n^{{th}{~}} minute. If a_{1} = a_{2} = = a_{10} = 150 and a_{10},a_{11}, are in an A.P. with common difference -2 , then the time taken by him to count all notes is: Sequence & Series (Mathematics)

A person is to count 4500 currency notes. Let

a_{n}

denote the number of notes he counts in the

n^{\text{th}\text{~}}

minute. If

a_{1} = a_{2} = \ldots = a_{10} = 150

and

a_{10},a_{11},\ldots

are in an A.P. with common difference -2 , then the time taken by him to count all notes is

If a_{n} = \frac{3}{4} - ( \frac{3}{4} )^{2} + ( \frac{3}{4} )^{3} + ( - 1)^{n - 1}( \frac{3}{4} )^{n} and b_{n} = 1 - a_{n}, then find the least natural number n_{0} such that b_{n} > a_{n}\forall n ? n_{0}

If a_1, a_2, a_n are in A.P. where a_i>0 for all i show that &\frac{1}{\sqrt{a_1}+\sqrt{a_2}}+\frac{1}{\sqrt{a_2}+\sqrt{a_3}}+\cdots+\frac{1}{\sqrt{a_{n-1}}+\sqrt{a_n}}&=\frac{n-1}{\sqrt{a_1}+\sqrt{a_n}}

Let A_{1},G_{1} and H_{1} denote the arithmetic, geometric and harmonic means . respectively of two distinct positive numbers. For n ? 2 let A_{n - 1} and H_{n - 1} have . arithmetic, geometric and harmonic means as A_{n},G_{n},H_{n} respectively. Which of the following statements is correct?

If a_{1},a_{2},a_{3}, are in A.P. such that a_{1} + a_{7} + a_{16} = 40, then the sum of the first 15 terms of this A.P. is

Number of 4 -digit numbers that are less than or equal to 2800 and either divisible by 3 or by 11 , is equal to

Let a,b be two non-zero real numbers. If p and r are the roots of the equation x^{2} - 8ax + 2a = 0 and q and s are the roots of the equation \end{enumerate} x^{2} + 12bx + 6b = 0, such that \frac{1}{p},\frac{1}{q},\frac{1}{r},\frac{1}{s} are in A.P., then a^{- 1} - b^{- 1} is equal to

The sum of the first n terms of the series (1^{2} + 2.2^{2} + 3^{2} + 2.4^{2} + 5^{2} + 2 . 6^{2} + ..) is (\frac{n(n + 1)^{2}}{2}, when n is even. when n is odd, the sum is

For any odd integer n ? 1,n^{3} - (n - 1)^{3} + + ( - 1)^{n - 1}1^{3} =

Different A.P. are constructed with the first term 100 , the last term 199, and integral common differences. The sum of the common differences of all such A.P. having at least 3 terms and at most 33 terms is

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