<u>Answer:</u>
B. He multiplied the dividend by 100 instead of 10.
<u>Step-by-step explanation:</u>
Chen had to divide by
. To make it easier to divide, he thought of multiplying both the dividend and the divisor by 10.
Chen multiplied the divisor by 10 but mistakenly multiplied the dividend by 100 instead of 10.
So his whole division problem was changed.
Therefore, the correct answer option is B. He multiplied the dividend by 100 instead of 10.
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Explanation:
a = 200 = first term
d = -30 = common difference
Tn = nth term
Tn = a + d(n-1)
Tn = 200 + (-30)(n-1)
Tn = 200 - 30n + 30
Tn = -30n + 230
Set Tn less than 0 and isolate n
Tn < 0
-30n + 230 < 0
230 < 30n
30n > 230
n > 230/30
n > 7.667 approximately
Rounding up to the nearest whole number gets us
So Tn starts to turn negative when n = 8
We can see that,
Tn = -30n + 230
T7 = -30*7 + 230
T7 = 20
and
Tn = -30n + 230
T8 = -30*8 + 230
T8 = -10 is the 8th term
and lastly
Tn = -30n + 230
T9 = -30*9 + 230
T9 = -40 is the ninth term
Or once you determine that T7 = 20, you subtract 30 from it to get 20-30 = -10 which is the value of T8. Then T9 = -40 because -10-30 = -40.