Let total vehicles on road excluding crane = 2n + 1.
Vehicles on both sides of larger vehicle = n + n.
Distance covered in lifting vehicles by crane between P and M.
Sn = 10n + 2[10(n – 1) + 10(n – 2) + ………..+10 × 2 + 10 × 1]
Similar, Distance covered in lifting vechiles between Q and M.
Sn‘ = 2[10n + 10(n – 1) + 10(n – 2) + ………+10 × 2 + 10 × 1]
Total distance covered
S = Sn + Sn
∵ Since crane covered 3000 m (3 km) distance in total.
∴ 20n2 + 10n = 3000
⇒ 2n2 + n – 300 = 0
⇒ (n – 12)(2n + 25) = 0
∵ n ≠ -ive
n – 12 = 0
∴ 2n + 1 = 2 × 12 + 1 = 25
Hence, there, are total 26(25 + 1) vehicles including crane.