Gabby left home at 11.25 a.m. and drove towards the seaside resort. 2 hours later, her grandfather left their home and drove towards the same seaside resort at 88 km/h. When the grandfather reached the seaside resort at 4.25 p.m., Gabby had another 5 km to travel. What was Gabby’s average speed? Express your answer in mixed number.
Time that the Gabby's grandfather started driving = 1.25 p.m.
Duration that Gabby's grandfather drove from 1.25 p.m. to 4.25 p.m. = 3 h

Distance that Gabby's grandfather travelled
= 3 x 88
= 264 km

Distance that Gabby travelled by the time her grandfather reached the city
= 264 - 5
= 259 km

Time that Gabby took to travel 259 km = 5 h

Gabby's average speed
= 259 ÷ 5
= 51⁴₅ km/h

Answer(s): 51⁴₅ km/h