☰ Year plan · Mathematics

Egyptian banknotes

Week 16 · Egyptian banknotes · 3 lessons
2

Making 20, 50 and 100 pounds

Discover Mathematics P2: Term 2, Lessons 61–70
GoalMake 20, 50 and 100 LE in different ways with banknotes and check by adding.
New words
amount · how much money in allcombination · a group of notes put togethermake an amount · choose notes whose values add up to it
Explanation

The same amount can be made with different notes. To make 20 LE you can use one 20 LE note, or two 10 LE notes. To make 50 LE you can use one 50 LE note, or two 20 LE notes and one 10 LE note, or five 10 LE notes. To make 100 LE you can use two 50 LE notes. Add the values to check: 20 + 20 + 10 = 50. For an amount like 28 LE, split it into 20 and 8: one 20 LE note and eight 1 LE notes. Start with the biggest note that fits, then use smaller ones.

NotesTotal
50 LE50 LE
20 + 20 + 1050 LE
10 + 10 + 10 + 10 + 1050 LE
Worked examples
20 LE20 LE10 LE
Make 50 LE: 20 + 20 = 40, and 40 + 10 = 50.
50 LE50 LE
Make 100 LE with two notes: 50 + 50 = 100.
50 LE20 LE20 LE10 LE
Make 100 LE with four notes: 50 + 20 = 70, 70 + 20 = 90, 90 + 10 = 100.
Class activity

Banker game. Take turns to be the banker. The banker says 20, 50 or 100. The other player makes that amount from play money in two different ways. Add the notes out loud to check each way.

Practice
1
Make 20 LE using only 10 LE notes. How many notes do you need?
2
Mina says that these notes make 50 LE. Is she right?
20 LE10 LE10 LE
3
Which pair of notes makes 70 LE: 50 LE and 20 LE, or 20 LE and 20 LE?
4
Karim has these notes and wants 100 LE. How much more does he need?
50 LE20 LE20 LE
5
Farida says that 35 LE is one 20 LE note, one 10 LE note and five 1 LE notes. Is she right?