In Bolandia, the streets are constructed from 10-metre pieces. A lamppost must be placed at both ends of every completed street and at points every 10 metres along its length. Additional
lampposts must also be placed at every notice board along the road.
Einstein Street, in Bolandia, has 7 notice boards, and 42 lampposts were needed altogether.
How long is Einstein Street?
A 330 metres
B 340 metres
C 350 metres
D 360 metres

340m

Explanation:

Given that:

Streets are constructed from 10 m pieces;

A lamppost is placed at both ends and at every 10 m along its length ;

A lamppost is also placed at every notice board along its length :

Given that:

Einstein Street has 42 lamppost and 7 notice boards :

So,

7 lamppost for 7 notice boards :

Lamppost left = 42 - 7 = 35 lamppost

2 lamppost placed at both ends :

Lamppost left = 35 - 2 = 33 lamppost

Hence, the remaining is placed at 10 m along its length:

Hence, length of Einstein street :

33 lamppost each placed 10m from the starting lamppost = (33 * 10) = 330m

Distance between 33rd lamppost and the ending lamppost = 10m

Hence, total length = (330 + 10) = 340 m