one and half hour vs one and half hours

Some examples from the web:

• They usually leave like one and half hour ago.
• Stefan: Today we just had one and half hour of acceptable track conditions after this morning rain showers.
• Canciones del Bar is perfectly situated directly on the beach in downtown Jaco, Costa Rica. A short one and half hour scenic drive from the airport in San Jose, this beautiful appointed 15 unit facility is a true jewel.
• Only 40 mins from Dublin. One and half hours from Belfast.
• You'll have one and one half hours to build.
• I'll return in approximately one and one half hours.
• Leave to cook for about one and a half hours.
• Allow one and a half hours travelling time fromHobartto Port Arthur.
• After almost one and a half hours we reach Neuwerk - without crossing more dangerous shallows.
• The southern Molluccas (a one and one half hour presentation);
• Transamazonica 1975 (a one and one half hour presentation);
• Last Thursday speaking times were extremely tight and then suddenly we had between one and one-and-a-half hours when there was nothing on the agenda and we had to wait for the vote.
• The Conference of Presidents envisaged that Question Time would last one and a half hours; then the President reduced it to an hour.
• Still one and a half hours. just do anything.
• Place the crucible with its contents in the oven for one and a half hours at a temperature of 120 ºC.
• Enjoy a one and a half hour guided tour of a Tyrolean distillery. Passionate schnapps distillers from the Hall-Wattens region proudly present their expertise.
• We used to have one and a half hours with the Council at the beginning of the evening session.
• You had one and a half hours from 10:30 to finish that song.
• HE GIGGLES This television is going to be on one and a half hours every evening.
• I have been waiting for a reply for one and a half hours now.

Some examples from the web:

• They usually leave like one and half hour ago.
• You'll have one and one half hours to build.
• I'll return in approximately one and one half hours.
• Federico, if it's alright with you, I'll return in approximatly one and one half hours.
• Last Thursday speaking times were extremely tight and then suddenly we had between one and one-and-a-half hours when there was nothing on the agenda and we had to wait for the vote.
• The Conference of Presidents envisaged that Question Time would last one and a half hours; then the President reduced it to an hour.
• It's a one and a half hour trip.
• Place the crucible with its contents in the oven for one and a half hours at a temperature of 120 ºC.
• Still one and a half hours. just do anything.
• We used to have one and a half hours with the Council at the beginning of the evening session.
• There's about one and a half hours left at the West Coast polls.
• Theyll do for this one and a half hours.
• In about one and a half hours I am supposed to be flying to Croatia.
• I have been waiting for a reply for one and a half hours now.
• I regret that we are down to one hour rather than the usual one and a half hours.
• That poor little girl was waiting outside for one and a half hours!
• Heat the reaction flask (B) until the liquid boils and keep it boiling for one-and-a-half hours (¹).
• Place the double filter paper containing the residue on a watch glass and dry for one and a half hours in the air oven (4.3) 100 ºC ± 3 ºC.
• Heat the reaction flask (B) until the liquid boils and keep it boiling for one and a half hours(1).
• A reaction time of one and a half hours, is sufficient in the case of most of the organic substances in the presence of silver nitrate catalyst.