2 everywhere

2 x 50 = _ _ 0
Answer {E}

Ahem!Brent and Rahul, I think the question asked for ten's digit and NOT unit's digit!

vinay1983 wrote:Ahem!Brent and Rahul, I think the question asked for ten's digit and NOT unit's digit!

aah.. seems today's long bike ride has really played on my mind..

Is the Answer 8

22*49 + 2 == _ _ 8 0

vinay1983 wrote:Consider the following sequence : 2,22,222,2222,22222 etc. What is ten's digit of the sum of the first fifty terms of the sequence?

A. 2
B. 8
C. 6
D. 4
E. 0

Let K = the sum of the fifty terms.
To determine the tens digit of K, we need examine only the UNITS DIGITS and the TENS DIGITS of the 50 terms:

02 + 22 + 22 + .... + 22 + 22 + 22.

Note that all of the digits are the same except for one: the TENS digit of the first term = 0.

The sum of the 50 units digits = 50*2 = 100.
Thus, the units digit of K = 0.

When we calculate the tens digit of K, we must CARRY 10 from the units place.
The sum of the 50 tens digits + 10 carried from the units place = 0 + 49*2 + 10 = 108.
Thus, the tens digit of K = 8.

The correct answer is B.

Can i try to elaborate little simpler -

2, 22, 222 up to 50 terms ,

so unit digit - 50X 2 = 100 for sure
10 will carry forward
next 2 X 49 = ... 8

so ,,,8 + 10 = always 8 on right side

so ans must be 8

IMO - B

Yes the OA is 8