Ahigh gold-quartz ore contains is 0.25% gold by mass. how many grams of gold are in 1.25 tons of this ore?

Assuming a ton is 2,000 lbs use the following equation to figure out how many grams of gold by mass there is:
***NOTE*** if this is a metric ton then the conversion will be 1 metric ton = 1000 kg

1.25 tons x 2000 lb/ton = 2,500 lbs
2,500 lbs x .4535 kg/lbs = 1133.75kg x 1000 g/kg = 1,133,750 g
IF METRIC TON then 1.25 x 1000 = 1250 x 1000g/kg = 1,250,000 g

because it says 0.25% and a pecent is out of a 100, you must divide that percentage by 100 
use fraction of: 0.25%/100 = 0.0025

(easy way to think about this is if it were 50% gold by mass, then you would multiple the total tonnage by .5 (50/100 = .5), so 0.25% = 0.0025)

1,113,750g x .0025 = 2834 g of gold

if metric ton 1,250,000 x 0.0025 = 3125 g of ogld