Let the positive numbers `a , b , c , d` be in AP. Then `a b c ,a b d ,a c d ,b c d` are (2001, 1M) not in AP/GP/HP (b) in AP in GP (d) in HP

Options

A. HP
B. AP
C. GP
D. None of the above

Answer

A

Explanation

Given, a, b, c, d are in A.P.
`=(1)/(a),(1)/(b),(1)/(c),(1)/(d)` are in H.P.
`implies(1)/(d),(1)/(c),(1)/(b),(1)/(a)` are also in H.P.
Now, multiply each term by abcd.
`(abcd)/(d),(abcd)/(c),(abcd)/(b),(abcd)/(a)`
abc, abd, acd, bcd, are in H.P.