Comments on Diagnostic Exam and Reference Tables
Here, I’m talking about questions on the diagnostic exam that a good number
of people missed. Statistics are based on the 6th period class. (I never got
them for the 7th period class.)
I am assuming you have the exam and
the answer key to the exam.
I distributed these and checked multiple
times to be sure people had them. When you see something like: Q1 (16):
It means question 1, and that 16 out of 34 people got it wrong.
•
Q1(16): Counting sig digits.
•
Q2(14): Adding numbers and maintaining sig digits.
•
Q3(7): Multiplying numbers and maintaining sig digits.
1. If a number has a decimal point, scan the number from the left
until the first nonzero digit is encountered. Then count this and
all succeeding digits as significant.
2. If a number has
no
decimal point, scan the number from the right
until the first nonzero digit is encountered. Then count this and
all succeeding digits as significant.
3. When multiplying two numbers, the product has the same number
of sig digits as the factor with the least number of sig digits.
4. When adding or subtracting two numbers, the answer has sig dig
its such that it goes out to the same precision (i.e. decimal place)
as the addend with the least precision.
ex: 2
.
33

2
.
022 =
.
31.
Notice that something with 3 sig digits minus something with 4
sig digits, in this case, resulted in something with 2 sig digits. The
determining issue here is that we can only go to the hundredths
place. Another example: 7
.
23 + 93
.
2 = 100
.
4. Here, we can only
go to the tenths place. One more, 1300+265 = 1600; here we can
only go to the hundreds place.
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 Spring '08
 Staff
 Physics, Chemistry, Molecule, Ion, sig digits, N O2, ﬁrst nonzero digit

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