The following question is based on the five three-digit numbers given below:
$519, 368, 437, 246, 175$
Which of the following is the sum of the middle digits of the highest and the lowest numbers?

Choose the correct alternative to complete the series: $ba....b...aab....a...b$

Study the following arrangement carefully and answer the question.
$O, 4, E, J, 5, T, 1, A, M, Q, 3, 8, N, I, K, 7, W, F, 6, S, 9, U, 2, Y, X$
How many such numbers are there in the above arrangement,each of which is immediately preceded by a consonant and also immediately followed by a consonant?

Fill in the blank space for the given series with the correct alternative.
$6, 15, (\ldots), 45, 66, 91$

If $2$ is subtracted from each odd digit and $3$ is added to each even digit in the number $3675249$,how many digits will appear twice in the new number thus formed?

The positions of the first and the fifth digits in the number $53216894$ are interchanged. Similarly,the positions of the second and the sixth digits are interchanged,and so on. Which of the following will be the second from the right end after the rearrangement?