Point A, B , C and D lies on a straight line
AB : BD = 1:5
AC : CD = 7:11
Work out AB : BC : CD
A-C-D = 7:11 = 7 + 11 = 18 'units'
A-B-D = 1:5 = 3:15 = 18 'units'
AB : BC : CD = 3 : ? : 11 ? = 18-11-3 = 4
3:4:11
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