# Video: AF5P3-Q14-404135479658

π΄πΆ and π·πΉ are lines of length 18 units. (a) π΄π΅ : π΅πΆ = 2 : 7. Mark the point π΅ on the line π΄πΆ, using a cross. (b) π·πΈ : πΈπΉ = 1 : 3. Mark the point πΈ on the line π·πΉ, using a cross.

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### Video Transcript

π΄πΆ and π·πΉ are lines of length 18 units. Part a, the ratio π΄π΅ to π΅πΆ is two to seven. Mark the point π΅ on the line π΄πΆ using a cross. Part b, the ratio π·πΈ to πΈπΉ is one to three. Mark the point πΈ on the line π·πΉ using a cross.

Our ratio in part a is two to seven This means that we have a total of nine parts, as two plus seven is equal to nine. The length of the whole line π΄πΆ was equal to 18 units. Therefore, we can calculate the length of one part of the ratio by dividing 18 by nine. 18 divided by nine is equal to two. This represents one part of the ratio. The length π΄π΅ represented two parts. Therefore, we need to multiply two by two. This is equal to four. Therefore, π΄π΅ has length four units. The length π΅πΆ was represented by seven parts in the ratio. Therefore, we need to multiply seven by two. Seven multiplied by two is equal to 14. Therefore, the length on the line π΅πΆ is 14 units. Point π΅ lies on the line as shown. It is four units from π΄ and 14 units from πΆ.

We can now repeat this process for part b. This time the ratio of π·πΈ to πΈπΉ was one to three. This means that our first step is to add one and three. This equals four. So we have four parts in total. Once again, weβre told that π·πΉ is length 18 units. This means that we need to divide 18 by four. 18 divided by four is equal to 4.5. This means that one part in this case is equal to 4.5 units. The length π·πΈ was equal to one part of the ratio and one multiplied by 4.5 is equal to 4.5. The length of π·πΈ well therefore be equal to 4.5 units.

The length πΈπΉ was three parts of the ratio. We need to multiply three by 4.5. This is equal to 13.5. Therefore, the length πΈπΉ is 13.5 units. We can, therefore, mark point πΈ using a cross 4.5 units from π· and 13.5 units from πΉ. In both parts of the question, it is worth checking that our two lengths total 18. Four plus 14 is equal to 18, and 4.5 plus 13.5 is also equal to 18.