Not working "selected" attribute in "ion-selected" element in ionic 2 - angularjs

Question

I am using ionic 2 for making mobile application. When I use selected attribute in ion-select element its working for one page but when i am using it for another page(component)its not working .
I am new to Ionic-2
My code for working selected attribute is given below:
<ion-item>
<ion-label>IO/WBS</ion-label>
<ion-select interface="popover">
<ion-option value="Department1" selected>Department 1</ion-option>
<ion-option value="Department2 ">Department 2</ion-option>
<ion-option value="Department3 ">Department 3</ion-option>
</ion-select>
</ion-item>
<ion-item>
<ion-label>Approver</ion-label>
<ion-select interface="popover">
<ion-option value="Manager1" selected>Manager 1</ion-option>
<ion-option value="Manager2 ">Manager 2</ion-option>
<ion-option value="Manager3 ">Manager 3</ion-option>
</ion-select>
</ion-item>
</ion-list>
And my code for non-working "selected" in "ion-select" element is give below:
<ion-item>
<ion-label>Expense Details</ion-label>
<ion-select interface="popover" name="check" [(ngModel)]="check" (ionChange)="Change(check)">
<ion-option value="Bus fare" selected>Bas Fare</ion-option>
<ion-option value="Train Fare">Train Fare</ion-option>
<ion-option value="other">Other</ion-option>
</ion-select>
</ion-item>
<textarea id="box" rows=3 cols=35 style="display:none;text-align:center;" name="description" [(ngModel)]="description" ></textarea>
<ion-grid>
<ion-row>
<ion-col col-6>
<ion-label>Select Currency</ion-label>
<ion-select interface="popover" name="currency" [(ngModel)]="currency">
<ion-option value="INR" selected>INR</ion-option>
<ion-option value="GBP ">GBP</ion-option>
</ion-select>
</ion-col>
<ion-col col-6>
<ion-item>
<ion-label floating >Amount</ion-label>
<ion-input required type="number" name="amount" [(ngModel)]="amount"></ion-input >
</ion-item>
</ion-col>
</ion-row>
</ion-grid>
</ion-list>

Answer 1

I solved it for "Currency filed" by fixing it variable because
if you add ngModel then it won’t select any of them unless you set the variable to one of the values in the component.
for example :
this.dateExp = "";
this.check = "Bus fare";
this.amount = 0;
this.currency = "INR";
this.description =""
Its working for "INR" but not for Expense details Field .
Anybody suggest me !!!!