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. are in AP
B. are in GP
C. are in HP
D. are in none of the above progressions

Answer

C

Explanation

As given :a,b,c,d are in AP
`implies" "(1)/(a),(1)/(b),(1)/(c),(1)/(d)` are in HP
Multiplying by abcd throughout
`implies(abcd)/(a),(abcd)/(b),(abcd)/(c),(abcd)/(d),` are in HP
`implies" "bcd, abd, abc` are in HP.