One 100 foot roll of 50 grain primer cord is equal to how many pounds of dynamite?

• A. 3 lbs
• B. 9 lbs of dynamite
• C. 15 lbs
• D. 6 lbs

Answer: (B)

Focus on converting the detonating cord’s rated content to a dynamite mass. A roll rated at 50 grains per foot means each foot has 50 grains of explosive. For 100 feet, that’s 50 × 100 = 5,000 grains in total. Since 1 pound equals 7,000 grains, 5,000 grains is 5,000/7,000 pounds, which is about 0.71 pounds of dynamite. So the dynamite-equivalent for that 100-foot roll is roughly 0.7 pounds, not 9 pounds. If your answer choices don’t reflect this, the key idea is the conversion process: multiply length by grains per foot to get total grains, then divide by 7,000 to convert to pounds.