MathRevolution
--|---------|-----------------------|---------|-----------
A(1) B C D(2)
If AC=BD and AB=BC/3 in the number line, then what is the value of C?
A. 11/10
B. 19/10
C. 29/15
D. 6/10
E. 9/5
Attachment:
nmbrline.png [ 6.69 KiB | Viewed 5572 times ]
Assign numbers, starting with the most limiting factor: AB = BC/3,
BC = 3ABThe smaller number (AB) is usually easier. I chose 3, not 1, on purpose. I wanted segments to be in multiples of 3.
Let AB = 3. BC is three times that long. BC = 9
AC = BD means that
AB = CD. AC = BD because:
AD - AC = CD
AD - BD = AB
The two lengths being subtracted from the whole length AD are equal. Their differences, AB and CD, therefore are equal
AB = 3, so CD = 3 (and BD = 9) -- parts of ___
Now add, to see how many equal lengths the segment could be divided into: 3 + 9 + 3 = 15
If the line were divided into fifteenths, on the number line, letters would correspond to cardinal numbers in this way:
\(A = 1\frac{0}{15}, B = 1\frac{3}{15}, C = 1\frac{12}{15}, D = 1\frac{15}{15}\)Point C is at (\(1 + \frac{12}{15}\)) = \(1\frac{12}{15}\) = \(\frac{27}{15} = \frac{9}{5}\)
Answer: E