CAT Exam

The rightmost non zero digit of the number 30^2720 is
(1) 1
(2) 3
(3) 7
(4) 9

Read Solution (Total 2)

ans is (1)
30^2720
=(3*10)^2720
=3^2720*10^2720
10^2720 contains 2720 digits
now 3^2720 unit digit is 1 (3^4,3^8,3^12,...,3^2720 gives unit digit 1 )
so 1 is the rightmost non zero digit of the number 30^2720
11 years agoHelpfull: Yes(3) No(0)

1.
(3*10)^2720=((3^4)^680)*10^2720.81^any value will give 1 as unit digit. so the rightmost non zero digit will be 1.
11 years agoHelpfull: Yes(1) No(0)

CAT Other Question

Let S be the set of five digit numbers formed by the digits 1, 2, 3, 4 and 5, using each digit exactly once such that exactly two odd positions are occupied by odd digits. What is the sum of the digits in the rightmost position of the numbers in S?
(1) 228
(2) 216
(3) 294
(4) 192 Rectangular tiles each of size 70 cm by 30 cm must be laid horizontally on a rectangular floor of size 110 cm by 130 cm, such that the tiles do not overlap. A tile can be placed in any orientation so long as its edges are parallel to the edges of the floor. No tile should overshoot any edge of the floor. The maximum number of tiles that can be accommodated on the floor is
(1) 4
(2) 5
(3) 6
(4) 7