Answer:
They encircle the planet
times.
Step-by-step explanation:
Consider the provided information.
We have 2.5 mole of dust particles and the Avogadro's number is 
Thus, the number of dust particles is:

Diameter of a dust particles is 10μm and the circumference of earth is 40,076 km.
Convert the measurement in meters.
Diameter: 
If we line up the particles the distance they could cover is:

Circumference in meters:

Therefore,

Hence, they encircle the planet
times.
Answer:
Gabriel needs to have $3.75 for sales tax.
Step-by-step explanation:
A sales tax rate of 6.25% means that 6.25 cents is going to be charged for tax for each dollar you spend. (Because 6.25% of $1.00 is 6.25 cents.)
If he was spending $10, the sales tax would be 62.5 cents (6.25 cents per dollar x 10 dollars). Since he is spending $60 on this item, the equation would be (6.25 cents per dollar x 60 dollars) (6.25 cents x 60 = 375 cents).
And 375 cents equals $3.75.