For positive integers n, the integer part of the nth term of sequence D equals n, while the infinite decimal part of the nth term is constructed in order out of the consecutive positive multiples of n, beginning with 2n. For instance, D_1 = 1.2345678…, while D_2 = 2.4681012… The sum of the first seven terms of sequence D is between: Choose the correct choice from the following answers.
A) 28 and 29	B) 29 and 30	C) 30 and 31	D) 31 and 32	E) 32 and 33
First, construct the first seven terms, though only out to a few decimal places, following the given pattern.   D_1 = 1.23…   D_2 = 2.46…   D_3 = 3.69…   D_4 = 4.812…   D_5 = 5.10…   D_6 = 6.12…   D_7 = 7.14…   Now, to add up the first seven terms, you should be strategic about how many decimal places to keep. You can drop the hundredths place and get a good approximation with the tenths place—and if you find the sum too close to a boundary between choices, then you can refine your answer if necessary.   1.2 + 2.4 + 3.6 + 4.8 + 5.1 + 6.1 + 7.1= 
<gadget id="calculator">1.2 + 2.4 + 3.6 + 4.8 + 5.1 + 6.1 + 7.1</gadget>
<output>30.3</output>
30.3   Including more decimal places would only add a couple of tenths to the sum—not enough to tip the sum over 31.   The correct answer is 30 and 31.
<result>C</result>
For positive integers n, the integer part of the nth term of sequence D equals n, while the infinite decimal part of the nth term is constructed in order out of the consecutive positive multiples of n, beginning with 2n. For instance, D_1 = 1.2345678…, while D_2 = 2.4681012… The sum of the first seven terms of sequence D is between: