Advertisements
Advertisements
प्रश्न
The sum of three numbers in A.P. is 12 and the sum of their cubes is 288. Find the numbers.
Advertisements
उत्तर
\[\text { Let the numbers be } (a - d), a, (a + d) . \]
\[\text { Sum } = a - d + a + a + d = 12\]
\[ \Rightarrow 3a = 12\]
\[ \Rightarrow a = 4\]
\[\text { Also }, (a - d )^3 + a^3 + (a + d )^3 = 288\]
\[ \Rightarrow a^3 - d^3 - 3 a^2 d + 3a d^2 + a^3 + a^3 + d^3 + 3 a^2 d + 3a d^2 = 288\]
\[ \Rightarrow 3 a^3 + 6a d^2 = 288\]
\[ \Rightarrow 3 \left( 4 \right)^3 + 6 \times 4 \times d^2 = 288\]
\[ \Rightarrow 192 + 24 d^2 = 288\]
\[ \Rightarrow 24 d^2 = 96\]
\[ \Rightarrow d^2 = 4\]
\[ \Rightarrow d = \pm 2\]
\[\text { When a = 4, d = 2, the numbers are } 2, 4, 6 . \]
\[\text { When a = 4, d = - 2, the numbers are } 6, 4, 2 .\]
APPEARS IN
संबंधित प्रश्न
How many terms of the A.P. -6 , `-11/2` , -5... are needed to give the sum –25?
The difference between any two consecutive interior angles of a polygon is 5°. If the smallest angle is 120°, find the number of the sides of the polygon.
Find the sum of integers from 1 to 100 that are divisible by 2 or 5.
if `a(1/b + 1/c), b(1/c+1/a), c(1/a+1/b)` are in A.P., prove that a, b, c are in A.P.
Let < an > be a sequence. Write the first five term in the following:
a1 = 1 = a2, an = an − 1 + an − 2, n > 2
The nth term of a sequence is given by an = 2n2 + n + 1. Show that it is not an A.P.
Find:
10th term of the A.P. 1, 4, 7, 10, ...
If (m + 1)th term of an A.P. is twice the (n + 1)th term, prove that (3m + 1)th term is twice the (m + n + 1)th term.
The first and the last terms of an A.P. are a and l respectively. Show that the sum of nthterm from the beginning and nth term from the end is a + l.
\[\text { If } \theta_1 , \theta_2 , \theta_3 , . . . , \theta_n \text { are in AP, whose common difference is d, then show that }\]
\[\sec \theta_1 \sec \theta_2 + \sec \theta_2 \sec \theta_3 + . . . + \sec \theta_{n - 1} \sec \theta_n = \frac{\tan \theta_n - \tan \theta_1}{\sin d} \left[ NCERT \hspace{0.167em} EXEMPLAR \right]\]
Three numbers are in A.P. If the sum of these numbers be 27 and the product 648, find the numbers.
Find the sum of the following serie:
101 + 99 + 97 + ... + 47
Find the sum of all odd numbers between 100 and 200.
Find the sum of all integers between 50 and 500 which are divisible by 7.
Solve:
1 + 4 + 7 + 10 + ... + x = 590.
If 12th term of an A.P. is −13 and the sum of the first four terms is 24, what is the sum of first 10 terms?
Find the sum of all two digit numbers which when divided by 4, yields 1 as remainder.
If the sum of a certain number of terms of the AP 25, 22, 19, ... is 116. Find the last term.
If \[\frac{1}{a}, \frac{1}{b}, \frac{1}{c}\] are in A.P., prove that:
\[\frac{b + c}{a}, \frac{c + a}{b}, \frac{a + b}{c}\] are in A.P.
If \[a\left( \frac{1}{b} + \frac{1}{c} \right), b\left( \frac{1}{c} + \frac{1}{a} \right), c\left( \frac{1}{a} + \frac{1}{b} \right)\] are in A.P., prove that a, b, c are in A.P.
A manufacturer of radio sets produced 600 units in the third year and 700 units in the seventh year. Assuming that the product increases uniformly by a fixed number every year, find (i) the production in the first year (ii) the total product in 7 years and (iii) the product in the 10th year.
Shamshad Ali buys a scooter for Rs 22000. He pays Rs 4000 cash and agrees to pay the balance in annual instalments of Rs 1000 plus 10% interest on the unpaid amount. How much the scooter will cost him.
A carpenter was hired to build 192 window frames. The first day he made five frames and each day thereafter he made two more frames than he made the day before. How many days did it take him to finish the job?
A man accepts a position with an initial salary of ₹5200 per month. It is understood that he will receive an automatic increase of ₹320 in the very next month and each month thereafter.
(i) Find his salary for the tenth month.
(ii) What is his total earnings during the first year?
Write the value of n for which n th terms of the A.P.s 3, 10, 17, ... and 63, 65, 67, .... are equal.
If m th term of an A.P. is n and nth term is m, then write its pth term.
If 7th and 13th terms of an A.P. be 34 and 64 respectively, then its 18th term is
If the sum of n terms of an A.P. be 3 n2 − n and its common difference is 6, then its first term is
Sum of all two digit numbers which when divided by 4 yield unity as remainder is
In the arithmetic progression whose common difference is non-zero, the sum of first 3 n terms is equal to the sum of next n terms. Then the ratio of the sum of the first 2 n terms to the next 2 nterms is
If a, b, c are in A.P. and x, y, z are in G.P., then the value of xb − c yc − a za − b is
If for an arithmetic progression, 9 times nineth term is equal to 13 times thirteenth term, then value of twenty second term is ____________.
If a1, a2, ..., an are in A.P. with common difference d (where d ≠ 0); then the sum of the series sin d (cosec a1 cosec a2 + cosec a2 cosec a3 + ...+ cosec an–1 cosec an) is equal to cot a1 – cot an
A man accepts a position with an initial salary of Rs 5200 per month. It is understood that he will receive an automatic increase of Rs 320 in the very next month and each month thereafter. What is his total earnings during the first year?
The sum of n terms of an AP is 3n2 + 5n. The number of term which equals 164 is ______.
