9 dived by 3 = 3
so he surfed for 3 hours = 1/3 of 9
and there are 6 hours left
so he spent 6 hours building a sandcastle
Answer:
B. $10 bag, $0.80 per pound
Step-by-step explanation:
10 / 8 = 0.80
25 / 15 = 1.67
0.80 is cheaper
Answer:
63
Step-by-step explanation:
Since a1=7 and the question is to find a9, you just have to multiply 7 and 9 which is 63
Answer: 4 years
Step-by-step explanation:
A(0) has to be amount at start. Assume that's 5mg
Then A(t) = 5×(0.5)^(0.25t) = 5×2^(-t/4),
(also known as 5 exp(-λ t) with λ = ln(2)/4, incidentally).
We need to such that A(t) = 2.5mg, or 2^(-t/4) is 1/2, which happens when -t/4 is -1, or t is 4.
Answer:
nwm
Step-by-step explanation: