JAMB Geography 2021 Paper

Concept:Ground distance is found by multiplying map distance by the scale denominator and converting centimetres to kilometres.Explanation:For map (a), the scale is $1:100{,}000$, meaning $1$ cm on the map equals $100{,}000$ cm on the ground.Ground distance $= 10 \times 100{,}000 = 1{,}000{,}000$ cm.Since $100{,}000$ cm $= 1$ km, $1{,}000{,}000$ cm $= 10$ km.For map (b), the scale is $1:400{,}000$, meaning $1$ cm on the map equals $400{,}000$ cm on the ground.Ground distance $= 10 \times 400{,}000 = 4{,}000{,}000$ cm.Since $100{,}000$ cm $= 1$ km, $4{,}000{,}000$ cm $= 40$ km.Answer:The ground distances are $10$ km for map (a) and $40$ km for map (b). Therefore, the correct option is A. $10$ km, $40$ km.