tricky

615 - 74 - 93 = 448, the units digit of which is 8...

edge wrote:615 - 74 - 93 = 448, the units digit of which is 8...

sorry brother, i just edited my post as 615 is actually 6^15 means 6 to the power 15...same follows for others..please check the edited post...now try the question

Units digit of 6^15 is 6
Units digit of 7^4 is 1
Units digit of 9^3 is 9

So, (6^15)-(7^4)-(9^3)=(...xxxx6)-(2401)-(729)=6
Hence, the units digit is C

the upd (unit place digit) in 6 power 15 is 6 its really easy to know upds of any power by just knowing the recurring upd concept
as
6^1=6
6^2=36
6^3=216

so as and all

upd concept for 7 is
7^1=7
7^2=49
7^3=343
7^4=2401
7^5=16807
7^6=117649
7^7=823543
7^8=5764801

if u observe opds here u can simply say 7,9,3,1 are coming
so for all natural numbers in the power of 7 divisible by 4 (4,8,12,16......) we get upd as 1
for numbers when divided by 4 gives reminder 1 ( 1,5,9,13........) we get upd as 7
for nums when div by 4 gives reminder 2 (2,6,10,14..........) we get upd as 9
for nums when divided by 4 gives reminder 3 (3,7,11,15.........) we get upd as 3

so in this case upd is 1

so like same in the case of 9^3 upd is 9

now come to prob by their upds

6-1-9=5-9=15-9=6

so the ans is 6[/b][/i]

To summarize:

0: 0, 0, 0, 0
1: 1, 1, 1, 1
2: 2, 4, 8, 6
3: 3, 9, 7, 1
4: 4, 6, 4, 6
5: 5, 5, 5, 5
6: 6, 6, 6, 6
7: 7, 9, 3, 1
8: 8, 4, 2, 6
9: 9, 1, 9, 1

You can practice recalling the patterns for each digit while on the train or doing something else. They all repeat after 1, 2, or 4. All you need to remember to go from one to the next is the previous one's digit. So, don't worry about

7^1=7
7^2=49
7^3=343
7^4=2401
7^5=16807
7^6=117649
7^7=823543
7^8=5764801

Just think
7^1= 7
7^2= 49
7^3= 7 * 9 = 63
7^4= 7 * 3 = 21
7, 9, 3, 1