First find the total number of purple beads Carly needs: 50 rows * 20 beads / row = 1000 beads. Then find the total number of blue beads Carly needs: 40 rows * 18 beads / row = 720 beads. Then add the number of each color she needs to find the total number she needs: 1000 beads + 720 beads + 80 beads = 1800 beads. Then divide the number of beads by 10 to find the cost: 1800 beads / 10 beads / $1 = $180.
The answer: 180
Reverse engineering the question: Carly is making a beaded corset. She's going to add 50 rows of purple beads with 20 beads per row, 40 rows of blue beads with 18 beads per row, and 80 gold beads. If beads cost $1 per 10 beads, how much do all the beads she bought cost?

Spongebob earned 30 x $2 = $60 for the burgers. He also earned 12 x $1.5 = $18 for the large fries. Therefore, Spongebob earned $60 + $18 = $78 for the day.
The answer: 78
Reverse engineering the question: Spongebob works in a burger shop. If he sells 30 burgers for $2 each and 12 large fries for $1.5. How much will Spongebob earn for the day?

The total number of girls in the choir is 80 + 10 = 90 girls. The total number of blondes in the choir after 10 more are added is 30 + 10 = 40 blonde - haired girls. From the total number, the number of black - haired girls is 90 - 40 = 50 black - haired - girls.
The answer: 50
Reverse engineering the question: Lizzy's school choir has a mixture of 80 blonde and black-haired girls. Their teacher decides to add 10 more girls to the choir, who turns out to be blonde. If there were 30 blonde-haired girls in the choir initially, how many black-haired girls are present?

Sam completes a widget every 10 minutes. When Jack helps they finish 2 in 15 minutes. Sam has finished 1 widget and has begun working on another one, and Jack finishes the second one at 15 minutes. So it takes Jack 15 minutes to complete a widget. Sam worked for 6 hours yesterday, so he was able to complete 6 hours * 60 minutes per hour / 10 minutes per widget = 36 widgets. Jack worked for 4 hours, so he was able to complete 4 hours * 60 minutes per hour / 15 minutes per widget = 16 widgets. Sam, Jack, and Tony were able to complete 68 widgets together. So of those, Tony personally completed 68 widgets - 36 widgets - 16 widgets = 16 widgets. It took Tony 8 hours to complete those 16 widgets, so he takes 8 hours * 60 minutes per hour / 16 widgets = 30 minutes per widget.
The answer: 30
Reverse engineering the question:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Sam works at the Widget Factory, assembling Widgets. He can assemble 1 widget every 10 minutes. Jack from the loading dock can help assemble widgets when he doesn't have anything else to do. When he helps, they put together 2 complete widgets every 15 minutes. Recently the factory hired Tony to help assemble widgets. Being new to the job, he doesn't work as fast as Sam or Jack. Yesterday Sam worked for 6 hours before he had to leave work early for a dentist appointment. Jack was able to help out for 4 hours before he had to go back to the loading dock to unload a new shipment of widget materials. Tony worked the entire 8-hour shift. At the end of the day, they had completed 68 widgets. How long does it take Tony to assemble a Widget, in minutes?