# 3.MD.A.1 : Elapsed Time

## 3.MD.A.1: Elapsed Time

### Evidence Statement 3.C.6-2 Base explanations/reasoning on a number line.

### Samantha's Day

## Part A

The analog clock shows the time school begins.

An analog clock showing 8:50.

Plot the time school begins on the number line below.

This is a number line that goes from 8:00 a.m. to 10:00 a.m.. It is partitioned into 10 minute intervals.

## Part B

It takes Samantha twenty minutes to walk to school. At what time did Samantha leave her house to get to school on time? Use the number line to help explain your thinking.

Enter your answer and your explanation in the space provided.

## Part C

Samantha attends an assembly as soon as school begins. The assembly is 40 minutes long. At what time is the assembly over? Use the number line to help explain your thinking.

Enter your answer and your explanation in the space provided.

## Attribution

Clock picture,

## Student Copy

## Scoring Rubric

### Part A

Score of 1- Student response includes a mark on the number line provided indicating the correct time that school begins (8:50 a.m.).

Score of 0- Student response is incorrect.

### Scoring Rubric Part B

Score of 2- Student response includes the following 2 elements.

Computation component = 1 point

The student provides the correct time that Samantha would leave her house to get to school on time, 8:30 a.m.

Reasoning component = 1 point

The student provides a valid explanation using the number line.

Notes: If a computation mistake is made, credit cannot be given for the computation component, but 1 point can be given for a valid explanation.

Score of 1- Student response include 1 of the above elements.

Score of 0 - Student response is incorrect or irrelevant.

### Scoring Rubric Part C

Score of 2- Student response includes the following 2 elements.

Computation component = 1 point

The student provides the correct time that Samantha would leave the assembly, 9:30 a.m

Reasoning component = 1 point - The student provides a valid explanation using the number line.

Notes: If a computation mistake is made, credit cannot be given for the computation component, but 1 point can be given for a valid explanation.

Score of 1- Student response includes 1 of the above elements.

Score of 0- Student response is incorrect or irrelevant.