Why didn't I need to use else if statement in first block of code?

Here is the first block of code.

function assignment1() {
var number = prompt("Enter a number");
if (number>=1 && number<=10) {
    alert("The number is between 1 and 10.")
        }
if (number>=11 && number<=20) {
    alert("The number is between 11 and 20.")
        }
}
assignment1();

Here is the second.

function assignment2() {
var number = prompt("Enter a number");
if (number<50 || number>200) {
    alert("valid number!")
        }
else if (number>=50 || number<=200) {
    alert("good number!")
        }
}
assignment2();

Both blocks of code are working fine, however I'm just wondering why I had to use a else if statement for the 2nd and not the 1st.