Original Promptlook at this activity and then create a "detective' challenge card: "Challenge Cards"
Get within 20 of the target.
Get as close as possible without exceeding the target.
Your calculation must contain exactly two regroupings.
Predict whether your result will be above or below the target and justify your prediction.
Find the closest possible solution and prove that no other arrangement is closer.
This resource focuses on the concept of subtraction with an emphasis on cases that require double regrouping. Students are tasked with solving subtraction problems that meet specific target numbers using two regroupings, while also justifying their predictions through rounding and estimation. Each case provides a target number along with a set of digits that can be used for the calculation. Students are encouraged to demonstrate their understanding by constructing mathematical proofs to explain why their solution is the closest match to the target. Additionally, there's a creative assignment allowing students to design their own subtraction case with specific requirements.