Question 496 of 519MediumMCQ
If a1, a2, a3 ...... and b1, b2, b3 ....... are A.P., and a1 = 2, a10 = 3, a1b1 = 1 = a10b10, then a4 b4 is equal to -
Solutions · 1
Official solution
a1, a2, a3 .... are in A.P. (Let common difference is d1)
b1, b2, b3 .... are in A.P. (Let common difference is d2)
and a1 = 2, a10 = 3, a1b1 = 1 = a10b10
\[\because\] a1b1 = 1
\[\therefore\] b1 = \[{1 \over 2}\]
a10b10 = 1
\[\therefore\] b10 = \[{1 \over 3}\]
Now, a10 = a1 + 9d1 \[\Rightarrow\] d1 = \[{1 \over 9}\]
b10 = b1 + 9d2 \[\Rightarrow\] d2 = \[{1 \over 9}\] [31−21]=−541Now, a4 = 2 +93=37b4 =21−543=94∴a4b4 =2728 Answer the question to unlock