Answer:
C-10
A-90
B-10
Step-by-step explanation:
For rounding off to nearest tens, we compare the last digit.
Answer:
Step-by-step explanation:
For a first order decay, fraction remaining = 0.5n where n = number of half lives elapsed.
fraction remaining = 55% = 0.55
0.55 = 0.5n
log 0.55 = n log 0.5
-0.2596 = -0.301 n
n = 0.8625 = # of half lives elapsed
0.8625 half lives x 2.5 billion years/half live = 2.16 billion years have elapsed = age of the rock
b) 0.15 = 0.5n
log 0.15 = n log 0.5
-0.824 = -0.301 n
n = 2.74 half lives
2.5 billion years/half life x 2.74 half lives = 6.85 billion years = age of rock
X=-9
subtract 6x from both sides to get x alone as -1x, subtract 2 from both sides to balance. -1x=9, or 1x=-9
The answer is 12:1
note: this is often read as "12 to 1"
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Explanation
We have exactly four card that are labeled "3" and 52 cards total. So there are 52-4 = 48 cards that are not labeled "3".
From here you write the ratio 48:4 to indicate the odds against drawing a 3. There are 48 ways to lose, 4 ways to win. You list the number of ways to lose first when it comes to "odds against" type of problems.
Next step is to reduce the ratio 48:4 to get 12:1, note how I divided both parts by the GCF 4
48/4 = 12
4/4 = 1
So thats how 48:4 reduces to 12:1
If you focus on one suit, say the spades, then we have 12 cards that arent a 3 of spades while exactly one card is a 3 of spades. This is one way to see why 12:1 is the answer. If you were saying this out loud to a friend, then you might say something like "the odds against drawing a three are 12 to 1".
