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Level Four > Geometry and Measurement

# Moana's Watch

Achievement Objectives:

Specific Learning Outcomes:

Convert seconds to minutes.

Subtract minutes and seconds using a 24-hour clock

Devise and use problem solving strategies to explore situations mathematically (be systematic).

Description of mathematics:

First the students have to know that there are 31 days in May, 60 minutes in an hour and 60 seconds in a minute. Then they have to realise that Moana’s watch will be showing less than 13:00:00. Hence they have to find out how much the watch has lost in 31 days and subtract that from 13:00:00.

Required Resource Materials:
digital watch (to pose the problem)
calendar
Copymaster of the problem (English)
Copymaster of the problem (Māori)
Activity:

### Problem

Moana set her digital watch at 13:00:00 on the last day of April. Unfortunately the watch loses 11 seconds a day. What is the time on Moana’s watch when it is 13:00:00 on the last day of May?

### Teaching sequence

1. Pose the problem. To capture the interest of the students you could personalise the problem by showing a digital watch and saying that it loses 11 seconds a day.
2. Check that the calendar is displayed so that the students can find out how many days there are in May.
3. As the students work on the problem ask questions that focus their thinking on the calculations that they are using.
How did you work out the number of seconds the watch had lost?
4. Encourage the students to record their solutions for display at the end of the class.
5. Share solutions.

#### Extension to the problem

What if the watch lost 11 seconds an hour. What would the time read on Moana's watch?

#### Solution to the problem

Since there are 31 days between the last day of April and the last day of May, Moana’s watch will have lost 31 x 11 = 341 seconds. To convert this into minutes, divide by 60. Hence 341 seconds = 5 minutes and 41 seconds. We now have to subtract 5 minutes 41 seconds from 13:00:00. This gives 12:54:19. This is the time on Moana’s watch.

AttachmentSize
Moana.pdf34.43 KB
MoanaMaori.pdf48.37 KB

## A thousand seconds

Use seconds, minutes and hours.

Discuss the size of a thousand

Read the time in digital or analogue form

Devise and use problem solving strategies

## Me he Karaka

This is a level 2 measurement strand activity from the Figure It Out series.

## Time Problems

Understand how positive and negative numbers can be used in an unusual practical problem.

Devise and use problem solving strategies to explore situations mathematically (guess and check, be systematic, look for patterns, draw a diagram, make a table, use algebra).

## Training

Use their own language to talk about features of a set of data.

Devise and use problem solving strategies (draw a picture, use equipment, think).