Unit 7 · Data and Percentage

Six-Digit Bike Lock — Find the Last Digit

Lesson 9 of 9

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About this lesson

A six-digit bike lock code. The middle two digits are the product of the first two. The last two are double the middle two. The first digit is 7 and all six digits are different. Only one value of the second digit makes everything work.

Chapters

0:00Introduction
0:21The Question
1:05Visualising the Bike Lock
1:24Translating the Rules into Maths
1:51Testing Candidates (Systematic Trial)
2:24Finding the Solution
2:55Exam Strategy – The "Fail Fast" Method

Question

I have a six-digit code for my bike lock.

The two-digit number formed by the middle two digits was the result of multiplying the first digit by the second digit.

The two-digit number formed by the last two digits of the code was double the number formed by the middle two digits.

The first digit was 7 and all six digits were different.

What is the last digit of the code for my bike lock?

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