Answer: -12
Work: Since -4 is in parentheses, I did -4 / 5 first. After doing the division, I had gotten -0.8. I multiplied -0.8 by 15, and had gotten -12.
120 grams half life at 45 days would be 60 then half life of 60 in another 45 days (90 total) should be 30 grams
Complete question is;
An online store receives customer satisfaction ratings between 0 and 100, inclusive. In the first 10 ratings the store received, the average (arithmetic mean) of the ratings was 75. What is the least value the store can receive for the 11th rating and still be able to have an average of at least 85 for the first 20 ratings?
Answer:
50
Step-by-step explanation:
We are told that In the first 10 ratings the store received arithmetic mean of the ratings = 75.
Thus;
Sum of the first 10 ratings = 75 × 10 = 750
Now, for the mean of the first 20 ratings to be at least 85, it means that the sum of the first 20 ratings would be; 85 × 20 = 1700
Thus, the sum of the next 10 ratings would be; 1700 − 750 = 950.
If maximum rating = 100, then the maximum possible value of the sum of the 12th to 20th ratings is given by;
9 × 100 = 900.
Now, in order to make the store have an average of at least 85 for the first 20 ratings, the least value for the 11th rating is;
950 − 900 = 50
Step-by-step explanation:
that is only possible, if we don't need to use a 2 and a 5 (but especially the 2) to create the 1 in the middle (log(10) = log(2×5) or log (5×2) = 1).
in other words, if the 1 in the middle is just a given, and does not use any of our digits for is creation, then a solution is possible.
first of all, the upper left corner has to be log(0⁰). we cannot use the digit 0 for anything else. and 0^n (except for n = 0) is not a valid argument for a logarithm.
log(0⁰) = 0 log(2×1) = 0.3... log(9/4) = 0.35...
log(1×2) = 0.3... 1 log(3×6) = 1.26...
log(7/3) = 0.37... log(4×5) = 1.3... log(6⁹) = 7.0...
but as soon as we need to build the center 1 by log(10), which takes then away one of the 2s (as the only way to build 10 by multiplication is 2×5 or 5×2), there is no possible solution.
