2. When it is $4 \mathrm{pm}$ in London, it is $5 \mathrm{pm}$ in Madrid and 8 am in San Francisco. Julio went to bed in San Francisco at 9 pm yesterday. What time was it in Madrid at that instant?
A 6 am yesterday
B 6 pm yesterday
C 12 noon yesterday
D 12 midnight
E 6 am today
Solution
E

Since it is $5 \mathrm{pm}$ in Madrid at the same time as it is $8 \mathrm{am}$ in San Francisco, Madrid is 9 hours ahead of San Francisco. Therefore, when Julio went to bed at $9 \mathrm{pm}$ yesterday in San Francisco, it was 9 hours later in Madrid and hence it was 6 am today.