900 detik + 45 menit = jam

900 detik = 1/4 jam = 15 menit
15 menit + 45 menit = 60 menit

1 menit = 60 detik maka,
900 detik : 60 = 15 menit

1 jam = 60 menit maka,
15 menit + 45 menit = 60 menit / (1Jam)