The road less traveled

Topic: Logic

Difficulty: 8/10

Hint in 3…..

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Lay the 15 cities on a straight line by marking an “x”

If there are 15 cities on a line,  14 roads are needed to connect the first city to  all the other cities.

Solution in 3…..

2………

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FULL SOLUTION

Step 1:Using the hint, you would have used up 14 roads which leaves you with 56

Step 2: The 2nd city(most left) would need another 13 roads as it is already connected to the one beside it.

Step 3: Using this pattern, the 3rd city would need another 12 and so on.

Step 4: Amounts of roads used = 14+13+12….+9 (Remember that you only have 70 roads)

Step 5: The number of cities connected to all the others = SIX  (1st:14, 2nd:13, 3rd:12 6th:9)