Computation of temperature using Temp Sensor Lm35 with LPC1768

Computation of temperature using Temp Sensor Lm35 with LPC1768

I have connected a LM35 to ADC channel 1 of LPC1768. getting a value of
306(adc reading).
Vref =5V For 12 bit ADC Step size = 5V/4096=1.22mV to calculate the output
voltage. Vout in mV = adc_reading*Step size = 306*1.22mV= 373.32mV
LM35 sensor gives an output of 10mV for every 1 degree centigrade. so the
measured temperature is = 373.32/10= 37 degree centigrade
But bangalore's temperature reading is 27 degree centigrade.
Referred Mazidi's AVR Microcontroller and Embedded Systems book, The
digital output from ADC is calculated by the below formula Vout = analog
input voltage/step size if Vout is calculated with the above formula then
o/p voltage is Vout = 306/1.22=250.819mV
Voltage to temperature conversion = 250.819mV/10mV = 25.08 degree centigrade.
Unable to figure out what is right. Kindly help. Sorry for this silly
question.
Also connected an LDR to ADC channel 0 of LPC1768. Calculated the measured
output voltage Vout = adc_reading*step size. for adc_reading = 55-> vout =
0.064713 adc_reading = 3245-> vout = 3.962149 adc_reading = 4095-> vout =
4.999995
May be you experts can throw some light on this. confused as to why i am
unable to get the right temperature as per my city.