Answer:
0.153
Step-by-step explanation:
It has been a long time since I've done this, so I hope it is correct:
cos = adjacent side / hypotenuse
cos x = 13 / 85 = 0.153
Percent increase/decrease is:
(Change/original amount)x100
(.25/2.35)x100= 10.6%
The price of fan was 20 Dollars 55 cents last week.
Step-by-step explanation:
Let,
The price last week = x
As the price is 27% lower than last week, therefore
(100%-27%) * Price last week = $15
73% * x = 15
Solving the percentage;

The price of fan was 20 Dollars 55 cents last week.
Keywords: Percentage, multiplication.
Learn more about percentages at:
#LearnwithBrainly
If 4 are $2.00 , then x3 to get 12 light bulbs and 2x3=6 so it's $6.00
1.326 grams of NH3 are required to produce 4.65 g of HF.
Step-by-step explanation:
Balanced chemical reaction is written first to know the number of moles taking part in original reaction.
NH3 +3 F2 ⇒3 HF + NF3
Given:
mass of HF = 4.65
First the number of moles of HF in 4.65 grams is calculated by using the formula:
number of moles (n) = 
atomic mass of HF = 20 grams/mole
putting the values in the above equation number of moles can be found.
n = 
= 0.235 moles of HF are given.
From the equation it can be said that:
1 mole of NH3 reacts to form 3 moles of HF
so, x moles of NH3 would react to form 0.235 moles of HF
= 
3x = 0.235
x = 
x = 0.078 moles of NH3 is required.
The moles are converted to mass by applying the formula:
mass = atomic mass X number of moles (atomic mass of NH3 = 17 grams/mole)
putting the values in the formula
mass = 17 X 0.078
mass = 1.326 grams