Each day at Dans new job, he earns $10 more than the day before. If h

target to determine is earning value of day 1
each day Dan earns $10 more than other day
so day 1 = x
day 2 = x+10
day 3 = x+30
so on till day 15 ; x+140
#1
His total earnings for the three most recent work days equal $690.
recent three days ; day 13,14,15 ; and day 14 value would be mean of 690 ; 690/3 ; $330
so day x+130=330
x= $200
sufficient
#2
His total earnings for the three most recent work days exceed his total earnings for the first three work days by $360
three most recent days salary
3x+ ( 120+130+140) ; 3x+ 390
and salary of first 3 days ; 3x+(10+20) ; 3x+30
we are given
3x+390=3x+30+360
value of x cannot be determined
insufficient
IMO A

Hi,Archit3110

I guess there are couple of mistakes (Not in the final answer though ),i have marked the errors in red in your quoted answer.
Day 3= x+20
and
690/3=230 and not 330.
Hence x=100.
However as far as it is DS,none of it would matter
Please correct me if i am wrong.

Note that the daily increase is consistent: he always earns $10 more each day. This is essentially a consecutive integer problem (although, in this case, there are increments of 10, not 1). Use f to represent Dan’s earnings on the first day. Express his earnings on subsequent days as f + 10, f + 20, f + 30, … f + 140.

(1) SUFFICIENT: This statement provides the sum of the most recent three days:

(f + 120) + (f + 130) + (f + 140) = $690
3f + 390 = $690
3f = $300
f = $100

Dan earned $100 on his first day.

(2) INSUFFICIENT: This statement provides the difference between the totals for the first three days and the last three days:

First three days = (f) + (f + 10) + (f + 20) = 3f + 30
Last three days = (f + 120) + (f + 130) + (f + 140) = 3f + 390
Last three days − First three days = (3f + 390) − (3f + 30) = $360

This statement is always true, regardless of how much Dan made on the first day. (This information can be determined from the question stem alone!)

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